func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n;     cin >> n;     set<char> s;     char ch;     int rep = 0;     for (int i = 0; i < n; i++) {       cin >> ch;       if (s.find(ch) != s.end()) rep++;       s.insert(ch);     }     if (26 - s.size() >= rep)       cout << rep;     else       cout <<  -1 ;   }   