diff --git a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/DynamicExtent.h b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/DynamicExtent.h
--- a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/DynamicExtent.h
+++ b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/DynamicExtent.h
@@ -53,6 +53,11 @@
 ///   (bufptr) // extent is unknown
 SVal getDynamicExtentWithOffset(ProgramStateRef State, SVal BufV);
 
+/// \returns The stored element count of the region represented by a symbolic
+/// value \p BufV.
+DefinedOrUnknownSVal getDynamicElementCountWithOffset(ProgramStateRef State,
+                                                      SVal BufV, QualType Ty);
+
 } // namespace ento
 } // namespace clang
 
diff --git a/clang/lib/StaticAnalyzer/Checkers/ExprInspectionChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/ExprInspectionChecker.cpp
--- a/clang/lib/StaticAnalyzer/Checkers/ExprInspectionChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/ExprInspectionChecker.cpp
@@ -325,12 +325,12 @@
 
 void ExprInspectionChecker::analyzerGetExtent(const CallExpr *CE,
                                               CheckerContext &C) const {
-  const MemRegion *MR = getArgRegion(CE, C);
-  if (!MR)
+  const Expr *Arg = getArgExpr(CE, C);
+  if (!Arg)
     return;
 
   ProgramStateRef State = C.getState();
-  DefinedOrUnknownSVal Size = getDynamicExtent(State, MR, C.getSValBuilder());
+  SVal Size = getDynamicExtentWithOffset(State, C.getSVal(Arg));
 
   State = State->BindExpr(CE, C.getLocationContext(), Size);
   C.addTransition(State);
@@ -338,12 +338,12 @@
 
 void ExprInspectionChecker::analyzerDumpExtent(const CallExpr *CE,
                                                CheckerContext &C) const {
-  const MemRegion *MR = getArgRegion(CE, C);
-  if (!MR)
+  const Expr *Arg = getArgExpr(CE, C);
+  if (!Arg)
     return;
 
-  DefinedOrUnknownSVal Size =
-      getDynamicExtent(C.getState(), MR, C.getSValBuilder());
+  ProgramStateRef State = C.getState();
+  SVal Size = getDynamicExtentWithOffset(State, C.getSVal(Arg));
   printAndReport(C, Size);
 }
 
@@ -362,8 +362,8 @@
 
   assert(!ElementTy->isPointerType());
 
-  DefinedOrUnknownSVal ElementCount =
-      getDynamicElementCount(C.getState(), MR, C.getSValBuilder(), ElementTy);
+  DefinedOrUnknownSVal ElementCount = getDynamicElementCountWithOffset(
+      C.getState(), C.getSVal(getArgExpr(CE, C)), ElementTy);
   printAndReport(C, ElementCount);
 }
 
diff --git a/clang/lib/StaticAnalyzer/Checkers/MPI-Checker/MPIChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/MPI-Checker/MPIChecker.cpp
--- a/clang/lib/StaticAnalyzer/Checkers/MPI-Checker/MPIChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/MPI-Checker/MPIChecker.cpp
@@ -161,20 +161,41 @@
       return;
     }
 
-    DefinedOrUnknownSVal ElementCount = getDynamicElementCount(
-        Ctx.getState(), SuperRegion, Ctx.getSValBuilder(),
-        CE.getArgExpr(1)->getType()->getPointeeType());
-    const llvm::APSInt &ArrSize =
-        ElementCount.castAs<nonloc::ConcreteInt>().getValue();
+    QualType ElemType = CE.getArgExpr(1)->getType()->getPointeeType();
+    ProgramStateRef State = Ctx.getState();
+    SValBuilder &SVB = Ctx.getSValBuilder();
+    ASTContext &ASTCtx = Ctx.getASTContext();
+
+    auto ElementCount =
+        getDynamicElementCountWithOffset(State, CE.getArgSVal(1), ElemType)
+            .getAs<nonloc::ConcreteInt>();
+    if (!ElementCount)
+      return;
+    const llvm::APSInt &ArrSize = ElementCount->getValue();
+
+    CharUnits ElemSizeInChars = ASTCtx.getTypeSizeInChars(ElemType);
+    int64_t ElemSizeInBits =
+        (ElemSizeInChars.isZero() ? 1 : ElemSizeInChars.getQuantity()) *
+        ASTCtx.getCharWidth();
+    const NonLoc MROffset =
+        SVB.makeArrayIndex(MR->getAsOffset().getOffset() / ElemSizeInBits);
 
+    SVal Count = CE.getArgSVal(0);
     for (size_t i = 0; i < ArrSize; ++i) {
       const NonLoc Idx = Ctx.getSValBuilder().makeArrayIndex(i);
-
-      const ElementRegion *const ER = RegionManager.getElementRegion(
-          CE.getArgExpr(1)->getType()->getPointeeType(), Idx, SuperRegion,
-          Ctx.getASTContext());
-
-      ReqRegions.push_back(ER->getAs<MemRegion>());
+      auto CountReached = SVB.evalBinOp(State, BO_GE, Idx, Count, ASTCtx.BoolTy)
+                              .getAs<DefinedOrUnknownSVal>();
+      if (CountReached && State->assume(*CountReached, true))
+        break;
+
+      auto ElementRegionIndex =
+          SVB.evalBinOp(State, BO_Add, Idx, MROffset, SVB.getArrayIndexType())
+              .getAs<NonLoc>();
+      if (ElementRegionIndex) {
+        const ElementRegion *const ER = RegionManager.getElementRegion(
+            ElemType, *ElementRegionIndex, SuperRegion, Ctx.getASTContext());
+        ReqRegions.push_back(ER);
+      }
     }
   } else if (FuncClassifier->isMPI_Wait(CE.getCalleeIdentifier())) {
     ReqRegions.push_back(MR);
diff --git a/clang/lib/StaticAnalyzer/Core/DynamicExtent.cpp b/clang/lib/StaticAnalyzer/Core/DynamicExtent.cpp
--- a/clang/lib/StaticAnalyzer/Core/DynamicExtent.cpp
+++ b/clang/lib/StaticAnalyzer/Core/DynamicExtent.cpp
@@ -30,7 +30,9 @@
   MR = MR->StripCasts();
 
   if (const DefinedOrUnknownSVal *Size = State->get<DynamicExtentMap>(MR))
-    return *Size;
+    if (auto SSize =
+            SVB.convertToArrayIndex(*Size).getAs<DefinedOrUnknownSVal>())
+      return *SSize;
 
   return MR->getMemRegionManager().getStaticSize(MR, SVB);
 }
@@ -40,6 +42,39 @@
                         SVB.getArrayIndexType());
 }
 
+static DefinedOrUnknownSVal getConstantArrayElementCount(SValBuilder &SVB,
+                                                         const MemRegion *MR) {
+  if (!MR)
+    return UnknownVal();
+  MR = MR->StripCasts();
+
+  const auto *TVR = MR->getAs<TypedValueRegion>();
+  if (!TVR)
+    return UnknownVal();
+
+  QualType Ty = TVR->getValueType();
+  if (const auto *ConstArrayTy =
+          dyn_cast_or_null<ConstantArrayType>(Ty->getAsArrayTypeUnsafe()))
+    return SVB.makeIntVal(ConstArrayTy->getSize(), false);
+
+  return UnknownVal();
+}
+
+static DefinedOrUnknownSVal
+getDynamicElementCount(ProgramStateRef State, SVal Size,
+                       DefinedOrUnknownSVal ElementSize) {
+  assert(!ElementSize.isZeroConstant() && "Non-zero element size expected");
+  if (Size.isUndef())
+    return UnknownVal();
+
+  SValBuilder &SVB = State->getStateManager().getSValBuilder();
+
+  auto ElementCount =
+      SVB.evalBinOp(State, BO_Div, Size, ElementSize, SVB.getArrayIndexType())
+          .getAs<DefinedOrUnknownSVal>();
+  return ElementCount ? *ElementCount : UnknownVal();
+}
+
 DefinedOrUnknownSVal getDynamicElementCount(ProgramStateRef State,
                                             const MemRegion *MR,
                                             SValBuilder &SVB,
@@ -47,13 +82,12 @@
   assert(MR != nullptr && "Not-null region expected");
   MR = MR->StripCasts();
 
-  DefinedOrUnknownSVal Size = getDynamicExtent(State, MR, SVB);
-  SVal ElementSize = getElementExtent(ElementTy, SVB);
+  DefinedOrUnknownSVal ElementSize = getElementExtent(ElementTy, SVB);
+  if (ElementSize.isZeroConstant())
+    return getConstantArrayElementCount(SVB, MR);
 
-  SVal ElementCount =
-      SVB.evalBinOp(State, BO_Div, Size, ElementSize, SVB.getArrayIndexType());
-
-  return ElementCount.castAs<DefinedOrUnknownSVal>();
+  return getDynamicElementCount(State, getDynamicExtent(State, MR, SVB),
+                                ElementSize);
 }
 
 SVal getDynamicExtentWithOffset(ProgramStateRef State, SVal BufV) {
@@ -79,6 +113,18 @@
                                SvalBuilder.getArrayIndexType());
 }
 
+DefinedOrUnknownSVal getDynamicElementCountWithOffset(ProgramStateRef State,
+                                                      SVal BufV,
+                                                      QualType ElementTy) {
+  SValBuilder &SVB = State->getStateManager().getSValBuilder();
+  DefinedOrUnknownSVal ElementSize = getElementExtent(ElementTy, SVB);
+  if (ElementSize.isZeroConstant())
+    return getConstantArrayElementCount(SVB, BufV.getAsRegion());
+
+  return getDynamicElementCount(State, getDynamicExtentWithOffset(State, BufV),
+                                ElementSize);
+}
+
 ProgramStateRef setDynamicExtent(ProgramStateRef State, const MemRegion *MR,
                                  DefinedOrUnknownSVal Size, SValBuilder &SVB) {
   MR = MR->StripCasts();
diff --git a/clang/test/Analysis/array-bound-v2-constraint-check.c b/clang/test/Analysis/array-bound-v2-constraint-check.c
--- a/clang/test/Analysis/array-bound-v2-constraint-check.c
+++ b/clang/test/Analysis/array-bound-v2-constraint-check.c
@@ -1,10 +1,10 @@
-// RUN: %clang_analyze_cc1 -analyzer-checker=core,alpha.security.ArrayBoundV2,debug.ExprInspection \
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,unix.Malloc,alpha.security.ArrayBoundV2,debug.ExprInspection \
 // RUN:   -analyzer-config eagerly-assume=false -verify %s
 
 void clang_analyzer_eval(int);
 void clang_analyzer_printState(void);
 
-typedef unsigned long long size_t;
+typedef typeof(sizeof(int)) size_t;
 const char a[] = "abcd"; // extent: 5 bytes
 
 void symbolic_size_t_and_int0(size_t len) {
@@ -83,6 +83,18 @@
   clang_analyzer_eval(len <= 2);              // expected-warning {{UNKNOWN}}
 }
 
+void *malloc(size_t);
+void free(void *);
+void symbolic_longlong_and_int0_dynamic_extent(long long len) {
+  char *b = malloc(5);
+  (void)b[len + 1]; // no-warning
+  // len: [-1,3]
+  clang_analyzer_eval(-1 <= len && len <= 3); // expected-warning {{TRUE}}
+  clang_analyzer_eval(0 <= len);              // expected-warning {{UNKNOWN}}
+  clang_analyzer_eval(len <= 2);              // expected-warning {{UNKNOWN}}
+  free(b);
+}
+
 void symbolic_longlong_and_int1(long long len) {
   (void)a[len]; // no-warning
   // len: [0,4]
diff --git a/clang/test/Analysis/flexible-array-members.c b/clang/test/Analysis/flexible-array-members.c
--- a/clang/test/Analysis/flexible-array-members.c
+++ b/clang/test/Analysis/flexible-array-members.c
@@ -44,20 +44,52 @@
   clang_analyzer_dump(clang_analyzer_getExtent(&fam));
   clang_analyzer_dump(clang_analyzer_getExtent(fam.data));
   // expected-warning@-2 {{4 S64b}}
-  // expected-warning@-2 {{Unknown}}
+  // expected-warning@-2 {{0 S64b}}
 
   FAM *p = (FAM *)alloca(sizeof(FAM));
   clang_analyzer_dump(clang_analyzer_getExtent(p));
   clang_analyzer_dump(clang_analyzer_getExtent(p->data));
-  // expected-warning@-2 {{4 U64b}}
-  // expected-warning@-2 {{Unknown}}
+  // expected-warning@-2 {{4 S64b}}
+  // expected-warning@-2 {{0 S64b}}
 
   FAM *q = (FAM *)malloc(sizeof(FAM));
   clang_analyzer_dump(clang_analyzer_getExtent(q));
   clang_analyzer_dump(clang_analyzer_getExtent(q->data));
-  // expected-warning@-2 {{4 U64b}}
-  // expected-warning@-2 {{Unknown}}
+  // expected-warning@-2 {{4 S64b}}
+  // expected-warning@-2 {{0 S64b}}
+  free(q);
+
+  q = (FAM *)malloc(sizeof(FAM) + sizeof(int) * 2);
+  clang_analyzer_dump(clang_analyzer_getExtent(q));
+  clang_analyzer_dump(clang_analyzer_getExtent(q->data));
+  // expected-warning@-2 {{12 S64b}}
+  // expected-warning@-2 {{8 S64b}}
   free(q);
+
+  typedef struct __attribute__((packed)) {
+    char c;
+    int data[];
+  } PackedFAM;
+
+  PackedFAM *t = (PackedFAM *)malloc(sizeof(PackedFAM) + sizeof(int) * 2);
+  clang_analyzer_dump(clang_analyzer_getExtent(t));
+  clang_analyzer_dump(clang_analyzer_getExtent(t->data));
+  // expected-warning@-2 {{9 S64b}}
+  // expected-warning@-2 {{8 S64b}}
+  free(t);
+}
+
+void test_too_small_base(void) {
+  typedef struct FAM {
+    long c;
+    int data[];
+  } FAM;
+  short s = 0;
+  FAM *p = (FAM *) &s;
+  clang_analyzer_dump(clang_analyzer_getExtent(p));
+  clang_analyzer_dump(clang_analyzer_getExtent(p->data));
+  // expected-warning@-2 {{2 S64b}}
+  // expected-warning@-2 {{-6 S64b}}
 }
 
 void test_zero_length_array_fam(void) {
@@ -70,19 +102,19 @@
   clang_analyzer_dump(clang_analyzer_getExtent(&fam));
   clang_analyzer_dump(clang_analyzer_getExtent(fam.data));
   // expected-warning@-2 {{4 S64b}}
-  // expected-warning@-2 {{Unknown}}
+  // expected-warning@-2 {{0 S64b}}
 
   FAM *p = (FAM *)alloca(sizeof(FAM));
   clang_analyzer_dump(clang_analyzer_getExtent(p));
   clang_analyzer_dump(clang_analyzer_getExtent(p->data));
-  // expected-warning@-2 {{4 U64b}}
-  // expected-warning@-2 {{Unknown}}
+  // expected-warning@-2 {{4 S64b}}
+  // expected-warning@-2 {{0 S64b}}
 
   FAM *q = (FAM *)malloc(sizeof(FAM));
   clang_analyzer_dump(clang_analyzer_getExtent(q));
   clang_analyzer_dump(clang_analyzer_getExtent(q->data));
-  // expected-warning@-2 {{4 U64b}}
-  // expected-warning@-2 {{Unknown}}
+  // expected-warning@-2 {{4 S64b}}
+  // expected-warning@-2 {{0 S64b}}
   free(q);
 }
 
@@ -97,19 +129,19 @@
   clang_analyzer_dump(clang_analyzer_getExtent(&likely_fam));
   clang_analyzer_dump(clang_analyzer_getExtent(likely_fam.data));
   // expected-warning@-2 {{8 S64b}}
-  // expected-warning@-2 {{Unknown}}
+  // expected-warning@-2 {{4 S64b}}
 
   FAM *p = (FAM *)alloca(sizeof(FAM));
   clang_analyzer_dump(clang_analyzer_getExtent(p));
   clang_analyzer_dump(clang_analyzer_getExtent(p->data));
-  // expected-warning@-2 {{8 U64b}}
-  // expected-warning@-2 {{Unknown}}
+  // expected-warning@-2 {{8 S64b}}
+  // expected-warning@-2 {{4 S64b}}
 
   FAM *q = (FAM *)malloc(sizeof(FAM));
   clang_analyzer_dump(clang_analyzer_getExtent(q));
   clang_analyzer_dump(clang_analyzer_getExtent(q->data));
-  // expected-warning@-2 {{8 U64b}}
-  // expected-warning@-2 {{Unknown}}
+  // expected-warning@-2 {{8 S64b}}
+  // expected-warning@-2 {{4 S64b}}
   free(q);
 #else
   FAM likely_fam;
@@ -121,13 +153,13 @@
   FAM *p = (FAM *)alloca(sizeof(FAM));
   clang_analyzer_dump(clang_analyzer_getExtent(p));
   clang_analyzer_dump(clang_analyzer_getExtent(p->data));
-  // expected-warning@-2 {{8 U64b}}
+  // expected-warning@-2 {{8 S64b}}
   // expected-warning@-2 {{4 S64b}}
 
   FAM *q = (FAM *)malloc(sizeof(FAM));
   clang_analyzer_dump(clang_analyzer_getExtent(q));
   clang_analyzer_dump(clang_analyzer_getExtent(q->data));
-  // expected-warning@-2 {{8 U64b}}
+  // expected-warning@-2 {{8 S64b}}
   // expected-warning@-2 {{4 S64b}}
   free(q);
 #endif
diff --git a/clang/test/Analysis/memory-model.cpp b/clang/test/Analysis/memory-model.cpp
--- a/clang/test/Analysis/memory-model.cpp
+++ b/clang/test/Analysis/memory-model.cpp
@@ -66,8 +66,8 @@
 
 void field_ptr(S *a) {
   clang_analyzer_dump(&a->f);             // expected-warning {{Element{SymRegion{reg_$0<S * a>},0 S64b,struct S}.f}}
-  clang_analyzer_dumpExtent(&a->f);       // expected-warning {{4 S64b}}
-  clang_analyzer_dumpElementCount(&a->f); // expected-warning {{1 S64b}}
+  clang_analyzer_dumpExtent(&a->f);       // expected-warning {{extent_$1{SymRegion{reg_$0<S * a>}}}}
+  clang_analyzer_dumpElementCount(&a->f); // expected-warning {{(extent_$1{SymRegion{reg_$0<S * a>}}) / 4U}}
 }
 
 void symbolic_array() {
@@ -90,7 +90,7 @@
 void symbolic_malloc() {
   int *a = (int *)malloc(12);
   clang_analyzer_dump(a);             // expected-warning {{Element{HeapSymRegion{conj}}
-  clang_analyzer_dumpExtent(a);       // expected-warning {{12 U64b}}
+  clang_analyzer_dumpExtent(a);       // expected-warning {{12 S64b}}
   clang_analyzer_dumpElementCount(a); // expected-warning {{3 S64b}}
   free(a);
 }
@@ -98,22 +98,22 @@
 void symbolic_alloca() {
   int *a = (int *)alloca(12);
   clang_analyzer_dump(a);             // expected-warning {{Element{HeapSymRegion{conj}}
-  clang_analyzer_dumpExtent(a);       // expected-warning {{12 U64b}}
+  clang_analyzer_dumpExtent(a);       // expected-warning {{12 S64b}}
   clang_analyzer_dumpElementCount(a); // expected-warning {{3 S64b}}
 }
 
 void symbolic_complex() {
   int *a = (int *)malloc(4);
-  clang_analyzer_dumpExtent(a);       // expected-warning {{4 U64b}}
+  clang_analyzer_dumpExtent(a);       // expected-warning {{4 S64b}}
   clang_analyzer_dumpElementCount(a); // expected-warning {{1 S64b}}
 
   int *b = (int *)realloc(a, sizeof(int) * 2);
-  clang_analyzer_dumpExtent(b);       // expected-warning {{8 U64b}}
+  clang_analyzer_dumpExtent(b);       // expected-warning {{8 S64b}}
   clang_analyzer_dumpElementCount(b); // expected-warning {{2 S64b}}
   free(b);
 
   int *c = (int *)calloc(3, 4);
-  clang_analyzer_dumpExtent(c);       // expected-warning {{12 U64b}}
+  clang_analyzer_dumpExtent(c);       // expected-warning {{12 S64b}}
   clang_analyzer_dumpElementCount(c); // expected-warning {{3 S64b}}
   free(c);
 }
@@ -123,7 +123,7 @@
   char *b = (char *)malloc(13);
 
   clang_analyzer_dump(clang_analyzer_getExtent(a)); // expected-warning {{13 S64b}}
-  clang_analyzer_dump(clang_analyzer_getExtent(b)); // expected-warning {{13 U64b}}
+  clang_analyzer_dump(clang_analyzer_getExtent(b)); // expected-warning {{13 S64b}}
   clang_analyzer_eval(clang_analyzer_getExtent(a) ==
                       clang_analyzer_getExtent(b));
   // expected-warning@-2 {{TRUE}}
@@ -155,3 +155,16 @@
 
   operator delete[](a, std::align_val_t(32));
 }
+
+int a[5][0];
+struct T {
+  int x[];
+};
+
+T t[5];
+void zero_sized_element() {
+  clang_analyzer_dumpExtent(a);       // expected-warning {{0 S64b}}
+  clang_analyzer_dumpElementCount(a); // expected-warning {{5 S64b}}
+  clang_analyzer_dumpExtent(t);       // expected-warning {{0 S64b}}
+  clang_analyzer_dumpElementCount(t); // expected-warning {{5 S64b}}
+}
diff --git a/clang/test/Analysis/mpichecker.cpp b/clang/test/Analysis/mpichecker.cpp
--- a/clang/test/Analysis/mpichecker.cpp
+++ b/clang/test/Analysis/mpichecker.cpp
@@ -272,6 +272,49 @@
   MPI_Wait(&rs.req2, MPI_STATUS_IGNORE);
 } // no error
 
+void nestedRequestWithCount() {
+  typedef struct {
+    MPI_Request req[3];
+    MPI_Request req2;
+  } ReqStruct;
+
+  ReqStruct rs;
+  int rank = 0;
+  double buf = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+
+  for (int i = 0; i < 3; ++i)
+    MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+                &rs.req[i]);
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+              &rs.req2);
+  MPI_Waitall(2, rs.req, MPI_STATUSES_IGNORE);
+  MPI_Waitall(1, rs.req + 2, MPI_STATUSES_IGNORE);
+  MPI_Wait(&rs.req2, MPI_STATUS_IGNORE);
+} // no error
+
+void nestedRequestWithCountMissingNonBlockingWait() {
+  typedef struct {
+    MPI_Request req[3];
+    MPI_Request req2;
+  } ReqStruct;
+
+  ReqStruct rs;
+  int rank = 0;
+  double buf = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+
+  for (int i = 0; i < 3; ++i)
+    MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+                &rs.req[i]);
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+              &rs.req2);
+  MPI_Waitall(1, rs.req, MPI_STATUSES_IGNORE);
+  // MPI_Waitall(1, rs.req + 1, MPI_STATUSES_IGNORE);
+  MPI_Waitall(1, rs.req + 2, MPI_STATUSES_IGNORE);
+  MPI_Wait(&rs.req2, MPI_STATUS_IGNORE);
+} // expected-warning{{Request 'rs.req[1]' has no matching wait.}}
+
 void singleRequestInWaitall() {
   MPI_Request r;
   int rank = 0;