func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n, k;     cin >> n;     cin >> k;     if (n < k) {       cout << -1;       return 0;     }     if (k == 1) {       if (n == 1)         cout <<  a ;       else         cout << -1;       return 0;     }     if (k == 2) {       for (int i = 0; i < n >> 1; i++) cout <<  ab ;       if (n & 1) cout <<  a ;       return 0;     } else {       string temp =  cdefghijklmnopqrstuvwxyz ;       for (int i = 0; i < (n - k + 2) >> 1; i++) cout <<  ab ;       if ((n - k + 2) & 1) cout <<  a ;       for (int j = 0; j < (k - 2); j++) cout << temp[j];     }     cout << endl;     return 0;   }   