func_code_string: #include <bits/stdc++.h>   using namespace std;   int n, k;   vector<char> s;   int main() {     cin >> n >> k;     if (k > n) {       cout << -1;       cin >> n;       return 0;     }     if (k == 1 && n > 1) {       cout << -1;       cin >> n;       return 0;     }     for (int i = 0; i < n; i++) {       if (i % 2 == 0) {         s.push_back( a );       } else {         s.push_back( b );       }     }     int x = 98 + k - 2;     for (int i = n - 1; i >= n - k + 2; i--) {       s[i] = (char)x;       x--;     }     for (int i = 0; i < n; i++) {       cout << s[i];     }     cin >> n;     return 0;   }   