func_code_string: #include <bits/stdc++.h>   using namespace std;   void scan(int &x) {     bool neg = false;     register int c;     x = 0;     c = getchar();     if (c ==  - ) {       neg = true;       c = getchar();     }     for (; (c > 47 && c < 58); c = getchar()) x = (x << 1) + (x << 3) + c - 48;     if (neg) x *= -1;   }   int main() {     string s;     cin >> s;     int k;     cin >> k;     int n = s.size();     if (k > n)       cout <<  impossible ;     else {       bool ch[26] = {false};       int cnt = 0;       for (int i = 0; i < n; i++) {         if (!ch[s[i] -  a ]) {           cnt++;           ch[s[i] -  a ] = true;         }       }       if (k - cnt >= 0)         cout << k - cnt;       else         cout <<  0 ;     }     return 0;   }   