Language: C++

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

int main(){
    int n,m,s;
    cin>>n;
    map<string,int> mp;
    for(int i=0;i<n;i++){
        cin>>s;
        mp[s]++;
    }
    cin>>m;
    for(int i=0;i<m;i++){
        cin>>s;
        mp[s]--;
    }
    m=0;
    for(auto x:mp) m=max(m,x.second);
    cout<<m<<endl;
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:10:11: error: no match for 'operator[]' (operand types are 'std::map<std::__cxx11::basic_string<char>, int>' and 'int')
   10 |         mp[s]++;
      |           ^
In file included from /usr/include/c++/14/map:63,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:152,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_map.h:504:7: note: candidate: 'std::map<_Key, _Tp, _Compare, _Alloc>::mapped_type& std::map<_Key, _Tp, _Compare, _Alloc>::operator[](const key_type&) [with _Key = std::__cxx11::basic_string<char>; _Tp = int; _Compare = std::less<std::__cxx11::basic_string<char> >; _Alloc = std::allocator<std::pair<const std::__cxx11::basic_string<char>, int> >; mapped_type = int; key_type = std::__cxx11::basic_string<char>]'
  504 |       operator[](const key_type& __k)
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_map.h:504:34: note:   no known conversion for argument 1 from 'int' to 'const std::map<std::__cxx11::basic_string<char>, int>::key_type&' {aka 'const std::__cxx11::basic_string<char>&'}
  504 |       operator[](const key_type& __k)
      |                  ~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_map.h:524:7: note: candidate: 'std::map<_Key, _Tp, _Compare, _Alloc>::mapped_type& std::map<_Key, _Tp, _Compare, _Alloc>::operator[](key_type&&) [with _Key = std::__cxx11::basic_string<char>; _Tp = int; _Compare = std::less<std::__cxx11::basic_string<char> >; _Alloc = std::allocator<std::pair<const std::__cxx11::basic_string<char>, int> >; mapped_type = int; key_type = std::__cxx11::basic_string<char>]'
  524 |       operator[](key_type&& __k)
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_map.h:524:29: note:   no known conversion for argument 1 from 'int' to 'std::map<std::__cxx11::basic_string<char>, int>::key_type&&' {aka 'std::__cxx11::basic_string<char>&&'}
  524 |       operator[](key_type&& __k)
      |                  ~~~~~~~~~~~^~~
a.cc:15:11: error: no match for 'operator[]' (operand types are 'std::map<std::__cxx11::basic_string<char>, int>' and 'int')
   15 |         mp[s]--;
      |           ^
/usr/include/c++/14/bits/stl_map.h:504:7: note: candidate: 'std::map<_Key, _Tp, _Compare, _Alloc>::mapped_type& std::map<_Key, _Tp, _Compare, _Alloc>::operator[](const key_type&) [with _Key = std::__cxx11::basic_string<char>; _Tp = int; _Compare = std::less<std::__cxx11::basic_string<char> >; _Alloc = std::allocator<std::pair<const std::__cxx11::basic_string<char>, int> >; mapped_type = int; key_type = std::__cxx11::basic_string<char>]'
  504 |       operator[](const key_type& __k)
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_map.h:504:34: note:   no known conversion for argument 1 from 'int' to 'const std::map<std::__cxx11::basic_string<char>, int>::key_type&' {aka 'const std::__cxx11::basic_string<char>&'}
  504 |       operator[](const key_type& __k)
      |                  ~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_map.h:524:7: note: candidate: 'std::map<_Key, _Tp, _Compare, _Alloc>::mapped_type& std::map<_Key, _Tp, _Compare, _Alloc>::operator[](key_type&&) [with _Key = std::__cxx11::basic_string<char>; _Tp = int; _Compare = std::less<std::__cxx11::basic_string<char> >; _Alloc = std::allocator<std::pair<const std::__cxx11::basic_string<char>, int> >; mapped_type = int; key_type = std::__cxx11::basic_string<char>]'
  524 |       operator[](key_type&& __k)
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_map.h:524:29: note:   no known conversion for argument 1 from 'int' to 'std::map<std::__cxx11::basic_string<char>, int>::key_type&&' {aka 'std::__cxx11::basic_string<char>&&'}
  524 |       operator[](key_type&& __k)
      |                  ~~~~~~~~~~~^~~