Language: C++

#include<bits/stdc++.h>
using namespace std;

int main(){
	string s;
  int n = s.length();
  int ans = 0;
  for(int i=0;i<n;i++){
    string k;
    k+=s[i];
  	for(int j=i+1;j<n;j++){
    	k+=s[j];
      	if(k%2019==0){
        	ans++;
        }
	}
  }
  cout<<ans;
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:13:13: error: no match for 'operator%' (operand types are 'std::string' {aka 'std::__cxx11::basic_string<char>'} and 'int')
   13 |         if(k%2019==0){
      |            ~^~~~~
      |            | |
      |            | int
      |            std::string {aka std::__cxx11::basic_string<char>}
In file included from /usr/include/c++/14/valarray:605,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:166,
                 from a.cc:1:
/usr/include/c++/14/bits/valarray_after.h:409:5: note: candidate: 'template<class _Dom1, class _Dom2> std::_Expr<std::__detail::_BinClos<std::__modulus, std::_Expr, std::_Expr, _Dom1, _Dom2>, typename std::__fun<std::__modulus, typename _Dom1::value_type>::result_type> std::operator%(const _Expr<_Dom1, typename _Dom1::value_type>&, const _Expr<_Dom2, typename _Dom2::value_type>&)'
  409 |     _DEFINE_EXPR_BINARY_OPERATOR(%, struct std::__modulus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:409:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   13 |         if(k%2019==0){
      |              ^~~~
/usr/include/c++/14/bits/valarray_after.h:409:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__modulus, std::_Expr, std::_Constant, _Dom, typename _Dom::value_type>, typename std::__fun<std::__modulus, typename _Dom1::value_type>::result_type> std::operator%(const _Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&)'
  409 |     _DEFINE_EXPR_BINARY_OPERATOR(%, struct std::__modulus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:409:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   13 |         if(k%2019==0){
      |              ^~~~
/usr/include/c++/14/bits/valarray_after.h:409:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__modulus, std::_Constant, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__modulus, typename _Dom1::value_type>::result_type> std::operator%(const typename _Dom::value_type&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  409 |     _DEFINE_EXPR_BINARY_OPERATOR(%, struct std::__modulus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:409:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int'
   13 |         if(k%2019==0){
      |              ^~~~
/usr/include/c++/14/bits/valarray_after.h:409:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__modulus, std::_Expr, std::_ValArray, _Dom, typename _Dom::value_type>, typename std::__fun<std::__modulus, typename _Dom1::value_type>::result_type> std::operator%(const _Expr<_Dom1, typename _Dom1::value_type>&, const valarray<typename _Dom::value_type>&)'
  409 |     _DEFINE_EXPR_BINARY_OPERATOR(%, struct std::__modulus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:409:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   13 |         if(k%2019==0){
      |              ^~~~
/usr/include/c++/14/bits/valarray_after.h:409:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__modulus, std::_ValArray, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__modulus, typename _Dom1::value_type>::result_type> std::operator%(const valarray<typename _Dom::value_type>&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  409 |     _DEFINE_EXPR_BINARY_OPERATOR(%, struct std::__modulus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:409:5: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int'
   13 |         if(k%2019==0){
      |              ^~~~
/usr/include/c++/14/valarray:1200:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__modulus, std::_ValArray, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__modulus, _Tp>::result_type> std::operator%(const valarray<_Tp>&, const valarray<_Tp>&)'
 1200 | _DEFINE_BINARY_OPERATOR(%, __modulus)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1200:1: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::valarray<_Tp>'
   13 |         if(k%2019==0){
      |              ^~~~
/usr/include/c++/14/valarray:1200:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__modulus, std::_ValArray, std::_Constant, _Tp, _Tp>, typename std::__fun<std::__modulus, _Tp>::result_type> std::operator%(const valarray<_Tp>&, const typename valarray<_Tp>::value_type&)'
 1200 | _DEFINE_BINARY_OPERATOR(%, __modulus)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1200:1: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::valarray<_Tp>'
   13 |         if(k%2019==0){
      |              ^~~~
/usr/include/c++/14/valarray:1200:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__modulus, std::_Constant, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__modulus, _Tp>::result_type> std::operator%(const typename valarray<_Tp>::value_type&, const valarray<_Tp>&)'
 1200 | _DEFINE_BINARY_OPERATOR(%, __modulus)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1200:1: note:   template argument deduction/substitution failed:
a.cc:13:14: note:   mismatched types 'const std::valarray<_Tp>' and 'int'
   13 |         if(k%2019==0){
      |              ^~~~