Language: C++

#include<bits/stdc++.h>
using namespace std;
long int sum[200005];
long int count[2020];
int main(){
    string S;
    cin >> S;
    int N=S.length();
    int i,j;
    long int ans=0;
    long int pow=10;
    sum[1]=S[N-1]-'0';
    count[sum[1]]++;
    for(i=1;i<N;i++){
        sum[i+1]=(sum[i]+(S[N-1-i]-'0')*pow)%2019;
        count[sum[i+1]]++;
        pow=(pow*10)%2019;
    }
    for(i=1;i<2019;i++)ans+=(count[i]*(count[i]-1))/2;
    ans+=count[0]+(count[0]*(count[0]-1))/2;
    cout << ans << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:13:5: error: reference to 'count' is ambiguous
   13 |     count[sum[1]]++;
      |     ^~~~~
In file included from /usr/include/c++/14/algorithm:86,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:1:
/usr/include/c++/14/pstl/glue_algorithm_defs.h:101:1: note: candidates are: 'template<class _ExecutionPolicy, class _ForwardIterator, class _Tp> __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, typename std::iterator_traits<_II>::difference_type> std::count(_ExecutionPolicy&&, _ForwardIterator, _ForwardIterator, const _Tp&)'
  101 | count(_ExecutionPolicy&& __exec, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value);
      | ^~~~~
In file included from /usr/include/c++/14/algorithm:61:
/usr/include/c++/14/bits/stl_algo.h:4025:5: note:                 'template<class _IIter, class _Tp> typename std::iterator_traits< <template-parameter-1-1> >::difference_type std::count(_IIter, _IIter, const _Tp&)'
 4025 |     count(_InputIterator __first, _InputIterator __last, const _Tp& __value)
      |     ^~~~~
a.cc:4:10: note:                 'long int count [2020]'
    4 | long int count[2020];
      |          ^~~~~
a.cc:16:9: error: reference to 'count' is ambiguous
   16 |         count[sum[i+1]]++;
      |         ^~~~~
/usr/include/c++/14/pstl/glue_algorithm_defs.h:101:1: note: candidates are: 'template<class _ExecutionPolicy, class _ForwardIterator, class _Tp> __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, typename std::iterator_traits<_II>::difference_type> std::count(_ExecutionPolicy&&, _ForwardIterator, _ForwardIterator, const _Tp&)'
  101 | count(_ExecutionPolicy&& __exec, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value);
      | ^~~~~
/usr/include/c++/14/bits/stl_algo.h:4025:5: note:                 'template<class _IIter, class _Tp> typename std::iterator_traits< <template-parameter-1-1> >::difference_type std::count(_IIter, _IIter, const _Tp&)'
 4025 |     count(_InputIterator __first, _InputIterator __last, const _Tp& __value)
      |     ^~~~~
a.cc:4:10: note:                 'long int count [2020]'
    4 | long int count[2020];
      |          ^~~~~
a.cc:19:30: error: reference to 'count' is ambiguous
   19 |     for(i=1;i<2019;i++)ans+=(count[i]*(count[i]-1))/2;
      |                              ^~~~~
/usr/include/c++/14/pstl/glue_algorithm_defs.h:101:1: note: candidates are: 'template<class _ExecutionPolicy, class _ForwardIterator, class _Tp> __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, typename std::iterator_traits<_II>::difference_type> std::count(_ExecutionPolicy&&, _ForwardIterator, _ForwardIterator, const _Tp&)'
  101 | count(_ExecutionPolicy&& __exec, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value);
      | ^~~~~
/usr/include/c++/14/bits/stl_algo.h:4025:5: note:                 'template<class _IIter, class _Tp> typename std::iterator_traits< <template-parameter-1-1> >::difference_type std::count(_IIter, _IIter, const _Tp&)'
 4025 |     count(_InputIterator __first, _InputIterator __last, const _Tp& __value)
      |     ^~~~~
a.cc:4:10: note:                 'long int count [2020]'
    4 | long int count[2020];
      |          ^~~~~
a.cc:19:40: error: reference to 'count' is ambiguous
   19 |     for(i=1;i<2019;i++)ans+=(count[i]*(count[i]-1))/2;
      |                                        ^~~~~
/usr/include/c++/14/pstl/glue_algorithm_defs.h:101:1: note: candidates are: 'template<class _ExecutionPolicy, class _ForwardIterator, class _Tp> __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, typename std::iterator_traits<_II>::difference_type> std::count(_ExecutionPolicy&&, _ForwardIterator, _ForwardIterator, const _Tp&)'
  101 | count(_ExecutionPolicy&& __exec, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value);
      | ^~~~~
/usr/include/c++/14/bits/stl_algo.h:4025:5: note:                 'template<class _IIter, class _Tp> typename std::iterator_traits< <template-parameter-1-1> >::difference_type std::count(_IIter, _IIter, const _Tp&)'
 4025 |     count(_InputIterator __first, _InputIterator __last, const _Tp& __value)
      |     ^~~~~
a.cc:4:10: note:                 'long int count [2020]'
    4 | long int count[2020];
      |          ^~~~~
a.cc:20:10: error: reference to 'count' is ambiguous
   20 |     ans+=count[0]+(count[0]*(count[0]-1))/2;
      |          ^~~~~
/usr/include/c++/14/pstl/glue_algorithm_defs.h:101:1: note: candidates are: 'template<class _ExecutionPolicy, class _ForwardIterator, class _Tp> __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, typename std::iterator_traits<_II>::difference_type> std::count(_ExecutionPolicy&&, _ForwardIterator, _ForwardIterator, const _Tp&)'
  101 | count(_ExecutionPolicy&& __exec, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value);
      | ^~~~~
/usr/include/c++/14/bits/stl_algo.h:4025:5: note:                 'template<class _IIter, class _Tp> typename std::iterator_traits< <template-parameter-1-1> >::difference_type std::count(_IIter, _IIter, const _Tp&)'
 4025 |     count(_InputIterator __first, _InputIterator __last, const _Tp& __value)
      |     ^~~~~
a.cc:4:10: note:                 'long int count [2020]'
    4 | long int count[2020];
      |          ^~~~~
a.cc:20:20: error: reference to 'count' is ambiguous
   20 |     ans+=count[0]+(count[0]*(count[0]-1))/2;
      |                    ^~~~~
/usr/include/c++/14/pstl/glue_algorithm_defs.h:101:1: note: candidates are: 'template<class _ExecutionPolicy, class _ForwardIterator, class _Tp> __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, typename std::iterator_traits<_II>::difference_type> std::count(_ExecutionPolicy&&, _ForwardIterator, _ForwardIterator, const _Tp&)'
  101 | count(_ExecutionPolicy&& __exec, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value);
      | ^~~~~
/usr/include/c++/14/bits/stl_algo.h:4025:5: note:                 'template<class _IIter, class _Tp> typename std::iterator_traits< <template-parameter-1-1> >::difference_type std::count(_IIter, _IIter, const _Tp&)'
 4025 |     count(_InputIterator __first, _InputIterator __last, const _Tp& __value)
      |     ^~~~~
a.cc:4:10: note:                 'long int count [2020]'
    4 | long int count[2020];
      |          ^~~~~
a.cc:20:30: error: reference to 'count' is ambiguous
   20 |     ans+=count[0]+(count[0]*(count[0]-1))/2;
      |                              ^~~~~
/usr/include/c++/14/pstl/glue_algorithm_defs.h:101:1: note: candidates are: 'template<class _ExecutionPolicy, class _ForwardIterator, class _Tp> __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, typename std::iterator_traits<_II>::difference_type> std::count(_ExecutionPolicy&&, _ForwardIterator, _ForwardIterator, const _Tp&)'
  101 | count(_ExecutionPolicy&& __exec, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value);
      | ^~~~~
/usr/include/c++/14/bits/stl_algo.h:4025:5: note:                 'template<class _IIter, class _Tp> typename std::iterator_traits< <template-parameter-1-1> >::difference_type std::count(_IIter, _IIter, const _Tp&)'
 4025 |     count(_InputIterator __first, _InputIterator __last, const _Tp& __value)
      |     ^~~~~
a.cc:4:10: note:                 'long int count [2020]'
    4 | long int count[2020];
      |          ^~~~~