Language: C++

#include <bits/stdc++.h>
#define rep(i, n) for(int i = 0; i < n; ++i)
using namespace std;

int main(){
  int n, m; scanf("%d %d", &n, &m);
  vector<priority_queue<int>> v(n);
  rep(i, m){
    int a, b; scanf("%d %d", &a, &b); --a; --b;
    v[a].push(b);
    v[b].push(a);
  }
  bool b = 0;
  for(int c: v[0]){
    if(v[c].top == n-1){
      b = 1;
      break;
    }
  }
  if(b) printf("POSSIBLE\n");
  else printf("IMPOSSIBLE\n");
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:14:17: error: no matching function for call to 'begin(std::priority_queue<int>&)'
   14 |   for(int c: v[0]){
      |                 ^
In file included from /usr/include/c++/14/bits/algorithmfwd.h:39,
                 from /usr/include/c++/14/bits/stl_algo.h:59,
                 from /usr/include/c++/14/algorithm:61,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:1:
/usr/include/c++/14/initializer_list:88:5: note: candidate: 'template<class _Tp> constexpr const _Tp* std::begin(initializer_list<_Tp>)'
   88 |     begin(initializer_list<_Tp> __ils) noexcept
      |     ^~~~~
/usr/include/c++/14/initializer_list:88:5: note:   template argument deduction/substitution failed:
a.cc:14:17: note:   'std::priority_queue<int>' is not derived from 'std::initializer_list<_Tp>'
   14 |   for(int c: v[0]){
      |                 ^
In file included from /usr/include/c++/14/string:53,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/bits/range_access.h:52:5: note: candidate: 'template<class _Container> constexpr decltype (__cont.begin()) std::begin(_Container&)'
   52 |     begin(_Container& __cont) -> decltype(__cont.begin())
      |     ^~~~~
/usr/include/c++/14/bits/range_access.h:52:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/range_access.h: In substitution of 'template<class _Container> constexpr decltype (__cont.begin()) std::begin(_Container&) [with _Container = std::priority_queue<int>]':
a.cc:14:17:   required from here
   14 |   for(int c: v[0]){
      |                 ^
/usr/include/c++/14/bits/range_access.h:52:50: error: 'class std::priority_queue<int>' has no member named 'begin'
   52 |     begin(_Container& __cont) -> decltype(__cont.begin())
      |                                           ~~~~~~~^~~~~
/usr/include/c++/14/bits/range_access.h:63:5: note: candidate: 'template<class _Container> constexpr decltype (__cont.begin()) std::begin(const _Container&)'
   63 |     begin(const _Container& __cont) -> decltype(__cont.begin())
      |     ^~~~~
/usr/include/c++/14/bits/range_access.h:63:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/range_access.h: In substitution of 'template<class _Container> constexpr decltype (__cont.begin()) std::begin(const _Container&) [with _Container = std::priority_queue<int>]':
a.cc:14:17:   required from here
   14 |   for(int c: v[0]){
      |                 ^
/usr/include/c++/14/bits/range_access.h:63:56: error: 'const class std::priority_queue<int>' has no member named 'begin'
   63 |     begin(const _Container& __cont) -> decltype(__cont.begin())
      |                                                 ~~~~~~~^~~~~
/usr/include/c++/14/bits/range_access.h:95:5: note: candidate: 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::begin(_Tp (&)[_Nm])'
   95 |     begin(_Tp (&__arr)[_Nm]) noexcept
      |     ^~~~~
/usr/include/c++/14/bits/range_access.h:95:5: note:   template argument deduction/substitution failed:
a.cc:14:17: note:   mismatched types '_Tp [_Nm]' and 'std::priority_queue<int>'
   14 |   for(int c: v[0]){
      |                 ^
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:166:
/usr/include/c++/14/valarray:1227:5: note: candidate: 'template<class _Tp> _Tp* std::begin(valarray<_Tp>&)'
 1227 |     begin(valarray<_Tp>& __va) noexcept
      |     ^~~~~
/usr/include/c++/14/valarray:1227:5: note:   template argument deduction/substitution failed:
a.cc:14:17: note:   'std::priority_queue<int>' is not derived from 'std::valarray<_Tp>'
   14 |   for(int c: v[0]){
      |                 ^
/usr/include/c++/14/valarray:1238:5: note: candidate: 'template<class _Tp> const _Tp* std::begin(const valarray<_Tp>&)'
 1238 |     begin(const valarray<_Tp>& __va) noexcept
      |     ^~~~~
/usr/include/c++/14/valarray:1238:5: note:   template argument deduction/substitution failed:
a.cc:14:17: note:   'std::priority_queue<int>' is not derived from 'const std::valarray<_Tp>'
   14 |   for(int c: v[0]){
      |                 ^
a.cc:14:17: error: no matching function for call to 'end(std::priority_queue<int>&)'
/usr/include/c++/14/initializer_list:99:5: note: candidate: 'template<class _Tp> constexpr const _Tp* std::end(initializer_list<_Tp>)'
   99 |     end(initializer_list<_Tp> __ils) noexcept
      |     ^~~
/usr/include/c++/14/initializer_list:99:5: note:   template argument deduction/substitution failed:
a.cc:14:17: note:   'std::priority_queue<int>' is not derived from 'std::initializer_list<_Tp>'
   14 |   for(int c: v[0]){
      |                 ^
/usr/include/c++/14/bits/range_access.h:74:5: note: candidate: 'template<class _Container> constexpr decltype (__cont.end()) std::end(_Container&)'
   74 |     end(_Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/bits/range_access.h:74:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/range_access.h: In substitution of 'template<class _Container> constexpr decltype (__cont.end()) std::end(_Container&) [with _Container = std::priority_queue<int>]':
a.cc:14:17:   required from here
   14 |   for(int c: v[0]){
      |                 ^
/usr/include/c++/14/bits/range_access.h:74:48: error: 'class std::priority_queue<int>' has no member named 'end'
   74 |     end(_Container& __cont) -> decltype(__cont.end())
      |                                         ~~~~~~~^~~
/usr/include/c++/14/bits/range_access.h:85:5: note: candidate: 'template<class _Container> constexpr decltype (__cont.end()) std::end(const _Container&)'
   85 |     end(const _Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/bits/range_access.h:85:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/range_access.h: In substitution of 'template<class _Container> constexpr decltype (__cont.end()) std::end(const _Container&) [with _Container = std::priority_queue<int>]':
a.cc:14:17:   required from here
   14 |   for(int c: v[0]){
      |                 ^
/usr/include/c++/14/bits/range_access.h:85:54: error: 'const class std::priority_queue<int>' has no member named 'end'
   85 |     end(const _Container& __cont) -> decltype(__cont.end())
      |                                               ~~~~~~~^~~
/usr/include/c++/14/bits/range_access.h:106:5: note: candidate: 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::end(_Tp (&)[_Nm])'
  106 |     end(_Tp (&__arr)[_Nm]) noexcept
      |     ^~~
/usr/include/c++/14/bits/range_access.h:106:5: note:   template argument deduction/substitution failed:
a.cc:14:17: note:   mismatched types '_Tp [_Nm]' and 'std::priority_queue<int>'
   14 |   for(int c: v[0]){
      |                 ^
/usr/include/c++/14/valarray:1249:5: note: candidate: 'template<class _Tp> _Tp* std::end(valarray<_Tp>&)'
 1249 |     end(valarray<_Tp>& __va) noexcept
      |     ^~~
/usr/include/c++/14/valarray:1249:5: note:   template argument deduction/substitution failed:
a.cc:14:17: note:   'std::priority_queue<int>' is not derived from 'std::valarray<_Tp>'
   14 |   for(int c: v[0]){
      |                 ^
/usr/include/c++/14/valarray:1265:5: note: candidate: 'template<class _Tp> const _Tp* std::end(const valarray<_Tp>&)'
 1265 |     end(const valarray<_Tp>& __va) noexcept
      |     ^~~
/usr/include/c++/14/valarray:1265:5: note:   template argument deduction/substitution failed:
a.cc:14:17: note:   'std::priority_queue<int>' is not derived from 'const std::valarray<_Tp>'
   14 |   for(int c: v[0]){
      |                 ^
a.cc:15:13: error: invalid use of member function 'std::priority_queue<_Tp, _Sequence, _Compare>::const_reference std::priority_queue<_Tp, _Sequence, _Compare>::top() const [with _Tp = int; _Sequence = std::vector<int>; _Compare = std::less<int>; const_reference = const int&]' (did you forget the '()' ?)
   15 |     if(v[c].top == n-1){
      |                ()