Language: C++

#include<bits/stdc++.h>
const int mod=1e9+7;
typedef long long ll;
const int N=2e5+5;
std::set<std::string> s;
int main()
{
	std::ios::sync_with_stdio(false);std::cin.tie(0);std::cout.tie(0);
	// freopen("a.in","r",stdin);
	// int T;scanf("%d",&T);while(T--){
	string s;cin>>s;
	int ans = 0;
	map<int,int>mp;
	int cnt = 0;
	mp[0] = 1;
	int bas = 1;
	for(int i = s.size() - 1; i >= 0; i--){
		ans = (ans + ll(s[i] - '0') * bas)%2019;
		cnt += mp[ans]++;
		bas = bas * 10 % 2019;
	}
	cout<<cnt<<endl;
	// }
	return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:11:9: error: 'string' was not declared in this scope
   11 |         string s;cin>>s;
      |         ^~~~~~
a.cc:11:9: note: suggested alternatives:
In file included from /usr/include/c++/14/string:41,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52,
                 from a.cc:1:
/usr/include/c++/14/bits/stringfwd.h:77:33: note:   'std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
/usr/include/c++/14/string:76:11: note:   'std::pmr::string'
   76 |     using string    = basic_string<char>;
      |           ^~~~~~
a.cc:11:18: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
   11 |         string s;cin>>s;
      |                  ^~~
      |                  std::cin
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:146:
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:13:9: error: 'map' was not declared in this scope
   13 |         map<int,int>mp;
      |         ^~~
a.cc:13:9: note: suggested alternatives:
In file included from /usr/include/c++/14/map:63,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:152:
/usr/include/c++/14/bits/stl_map.h:102:11: note:   'std::map'
  102 |     class map
      |           ^~~
/usr/include/c++/14/map:89:13: note:   'std::pmr::map'
   89 |       using map
      |             ^~~
a.cc:13:13: error: expected primary-expression before 'int'
   13 |         map<int,int>mp;
      |             ^~~
a.cc:15:9: error: 'mp' was not declared in this scope
   15 |         mp[0] = 1;
      |         ^~
a.cc:18:34: error: no match for 'operator[]' (operand types are 'std::set<std::__cxx11::basic_string<char> >' and 'int')
   18 |                 ans = (ans + ll(s[i] - '0') * bas)%2019;
      |                                  ^
a.cc:22:9: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   22 |         cout<<cnt<<endl;
      |         ^~~~
      |         std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:22:20: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   22 |         cout<<cnt<<endl;
      |                    ^~~~
      |                    std::endl
In file included from /usr/include/c++/14/istream:41,
                 from /usr/include/c++/14/sstream:40,
                 from /usr/include/c++/14/complex:45,
                 from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127:
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~