answer.code: In function ‘void solve()’:
answer.code:16:3: error: ‘map’ was not declared in this scope
   16 |   map<char,ll>f;
      |   ^~~
answer.code:7:1: note: ‘std::map’ is defined in header ‘<map>’; did you forget to ‘#include <map>’?
    6 | #include <utility>
  +++ |+#include <map>
    7 | using namespace std;
answer.code:16:7: error: expected primary-expression before ‘char’
   16 |   map<char,ll>f;
      |       ^~~~
answer.code:20:7: error: ‘f’ was not declared in this scope
   20 |       f[ch[i]]++;
      |       ^