Language: C++

#define _GLIBCXX_DEBUG
#include<algorithm>
#include<cmath>
#include<cstring>
#include<cstdio>
#include<iostream>
#include<vector>
#include<queue>
#include<deque>
#include<stack>
#include<set>
#include<map>
#include<string>
#include <bits/stdc++.h>
#define rep(i, n) for(int i = 0; i < (int)n; i++)
#define rep2(i,s,n) for(int i=s;i< (int)n; i++)
#define ll long long 
#define all(v) v.begin(),v.end()
using namespace std;
int main(){
  int n,m; cin >>n>>m;
  vector<int> a(m),b(m);
  rep(i,m) cin >>a[i]>>b[i];
  vector<vector<int>> c(n);
  rep(i,m) c[a[i]-1].push_back(b[i]);
  if(c[0].size()==0||c[0]==0) c[0].push_back(1);
  rep2(i,1,n) if(c[i].size()==0) c[i].push_back(0);
  int key=0;
  rep(i,n) rep(j,c[i].size()) if(c[i][j]!=c[i][0]) key=1;
  if(key==1) cout <<-1<<endl;
  else if(n==3) cout<<100*c[0][0]+10*c[1][0]+c[2][0]<<endl;
  else if(n==2) cout<<10*c[0][0]+c[1][0]<<endl;
  else cout <<c[0][0]<<endl;
}
  

Compiler output:
a.cc: In function 'int main()':
a.cc:26:26: error: no match for 'operator==' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::__debug::vector<int> >, std::__debug::vector<int> >::value_type' {aka 'std::__debug::vector<int>'} and 'int')
   26 |   if(c[0].size()==0||c[0]==0) c[0].push_back(1);
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181,
                 from a.cc:14:
/usr/include/c++/14/bits/regex.h:1103:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1103 |     operator==(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1103:5: note:   template argument deduction/substitution failed:
a.cc:26:28: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::__debug::vector<int> >, std::__debug::vector<int> >::value_type' {aka 'std::__debug::vector<int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   26 |   if(c[0].size()==0||c[0]==0) c[0].push_back(1);
      |                            ^
/usr/include/c++/14/bits/regex.h:1199:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator==(__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const sub_match<_BiIter>&)'
 1199 |     operator==(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1199:5: note:   template argument deduction/substitution failed:
a.cc:26:28: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::__debug::vector<int> >, std::__debug::vector<int> >::value_type' {aka 'std::__debug::vector<int>'} is not derived from 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'
   26 |   if(c[0].size()==0||c[0]==0) c[0].push_back(1);
      |                            ^
/usr/include/c++/14/bits/regex.h:1274:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator==(const sub_match<_BiIter>&, __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)'
 1274 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1274:5: note:   template argument deduction/substitution failed:
a.cc:26:28: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::__debug::vector<int> >, std::__debug::vector<int> >::value_type' {aka 'std::__debug::vector<int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   26 |   if(c[0].size()==0||c[0]==0) c[0].push_back(1);
      |                            ^
/usr/include/c++/14/bits/regex.h:1366:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1366 |     operator==(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1366:5: note:   template argument deduction/substitution failed:
a.cc:26:28: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   26 |   if(c[0].size()==0||c[0]==0) c[0].push_back(1);
      |                            ^
/usr/include/c++/14/bits/regex.h:1441:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1441 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1441:5: note:   template argument deduction/substitution failed:
a.cc:26:28: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::__debug::vector<int> >, std::__debug::vector<int> >::value_type' {aka 'std::__debug::vector<int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   26 |   if(c[0].size()==0||c[0]==0) c[0].push_back(1);
      |                            ^
/usr/include/c++/14/bits/regex.h:1534:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1534 |     operator==(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1534:5: note:   template argument deduction/substitution failed:
a.cc:26:28: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   26 |   if(c[0].size()==0||c[0]==0) c[0].push_back(1);
      |                            ^
/usr/include/c++/14/bits/regex.h:1613:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1613 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1613:5: note:   template argument deduction/substitution failed:
a.cc:26:28: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::__debug::vector<int> >, std::__debug::vector<int> >::value_type' {aka 'std::__debug::vector<int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   26 |   if(c[0].size()==0||c[0]==0) c[0].push_back(1);
      |                            ^
/usr/include/c++/14/bits/regex.h:2186:5: note: candidate: 'template<class _Bi_iter, class _Alloc> bool std::__cxx11::operator==(const match_results<_BiIter, _Alloc>&, const match_results<_BiIter, _Alloc>&)'
 2186 |     operator==(const match_results<_Bi_iter, _Alloc>& __m1,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:2186:5: note:   template argument deduction/substitution failed:
a.cc:26:28: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::__debug::vector<int> >, std::__debug::vector<int> >::value_type' {aka 'std::__debug::vector<int>'} is not derived from 'const std::__cxx11::match_results<_BiIter, _Alloc>'
   26 |   if(c[0].size()==0||c[0]==0) c[0].push_back(1);
      |                            ^
In file included from /usr/include/c++/14/vector:76,
                 from a.cc:7:
/usr/include/c++/14/debug/vector:871:5: note: candidate: 'template<class _Tp, class _Alloc> bool std::__debug::operator==(const vector<_Tp, _Alloc>&, const vector<_Tp, _Alloc>&)'
  871 |     operator==(const vector<_Tp, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/debug/vector:871:5: note:   template argument deduction/substitution failed:
a.cc:26:28: note:   mismatched types 'const std::__debug::vector<_Tp, _Alloc>' and 'int'
   26 |   if(c[0].size()==0||c[0]==0) c[0].push_back(1);
      |                            ^
In file included from /usr/include/c++/14/deque:77,
                 from /usr/include/c++/14/queue:62,
                 from a.cc:8:
/usr/include/c++/14/debug/deque:672:5: note: candidate: 'template<class _Tp, class _Alloc> bool std::__debug::operator==(const deque<_Tp, _Allocator>&, const deque<_Tp, _Allocator>&)'
  672 |     operator==(const deque<_Tp, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/debug/deque:672:5: note:   template argument deduction/substitution failed:
a.cc:26:28: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::__debug::vector<int> >, std::__debug::vector<int> >::value_type' {aka 'std::__debug::vector<int>'} is not derived from 'const std::__debug::deque<_Tp, _Allocator>'
   26 |   if(c[0].size()==0||c[0]==0) c[0].push_back(1);
      |                            ^
In file included from /usr/include/c++/14/debug/set:41,
                 from /usr/include/c++/14/set:69,
                 from a.cc:11:
/usr/include/c++/14/debug/set.h:611:5: note: candidate: 'template<class _Key, class _Compare, class _Allocator> bool std::__debug::operator==(const set<_Key, _Compare, _Allocator>&, const set<_Key, _Compare, _Allocator>&)'
  611 |     operator==(const set<_Key, _Compare, _Allocator>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/debug/set.h:611:5: note:   template argument deduction/substitution failed:
a.cc:26:28: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::__debug::vector<int> >, std::__debug::vector<int> >::value_type' {aka 'std::__debug::vector<int>'} is not derived from 'const std::__debug::set<_Key, _Compare, _Allocator>'
   26 |   if(c[0].size()==0||c[0]==0) c[0].push_back(1);
      |                            ^
In file included from /usr/include/c++/14/debug/set:42:
/usr/include/c++/14/debug/multiset.h:601:5: note: candidate: 'template<class _Key, class _Compare, class _Allocator> bool std::__debug::operator==(const multiset<_Key, _Compare, _Allocator>&, const multiset<_Key, _Compare, _Allocator>&)'
  601 |     operator==(const multiset<_Key, _Compare, _Allocator>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/debug/multiset.h:601:5: note:   template argument deduction/substitution failed:
a.cc:26:28: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::__debug::vector<int> >, std::__debug::vector<int> >::value_type' {aka 'std::__debug::vector<int>'} is not derived from 'const std::__debug::multiset<_Key, _Compare, _Allocator>'
   26 |   if(c[0].size()==0||c[0]==0) c[0].push_back(1);
      |                            ^
In file included from /usr/include/c++/14/debug/map:43,
                 from /usr/include/c++/14/map:69,
                 from a.cc:12:
/usr/include/c++/14/debug/map.h:748:5: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Allocator> bool std::__debug::operator==(const map<_Key, _Tp, _Compare, _Allocator>&, const map<_Key, _Tp, _Compare, _Allocator>&)'
  748 |     operator==(const map<_Key, _Tp, _Compare, _Allocator>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/debug/map.h:748:5: note:   template argument deduction/substitution failed:
a.cc:26:28: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::__debug::vector<int> >, std::__debug::vector<int> >::value_type' {aka 'std::__debug::vector<int>'} is not derived from 'const std::__debug::map<_Key, _Tp, _Compare, _Allocator>'
   26 |   if(c[0].size()==0||c[0]==0) c[0].push_back(1);
      |                            ^
In file included from /usr/include/c++/14/debug/map:44:
/usr/include/c++/14/debug/multimap.h:630:5: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Allocator> bool std::__debug::operator==(c