func_code_string: #include <bits/stdc++.h>   using namespace std;   const int MAXN = 2e3 + 10;   long long n, k;   char s[MAXN];   int num[33];   int main() {     while (cin >> s) {       cin >> k;       int len = strlen(s);       if (len < k) {         cout <<  impossible  << endl;       } else {         memset(num, 0, sizeof num);         for (int i = 0; i < len; ++i) {           num[s[i] -  a ]++;         }         long long ans = 0;         for (int i = 0; i < 26; ++i) {           if (num[i]) ++ans;         }         if (ans <= k)           cout << k - ans << endl;         else           cout << 0 << endl;       }     }     return 0;   }   