func_code_string: #include <bits/stdc++.h>   using namespace std;   char s[1000005];   int main() {     int n, k;     while (scanf( %d%d , &n, &k) != EOF) {       if (k > n || (n > 1 && k == 1)) {         printf( -1 n );         break;       } else {         if ((n - k) % 2) {           for (int i = 1; i <= n - k + 1; i++) {             s[i] =  a ;             s[i + 1] =  b ;             i++;           }           s[n - k + 2] =  a ;           int c = 99;           for (int i = n - k + 3; i <= n; i++) {             s[i] = c;             c++;           }         } else {           for (int i = 1; i <= n - k; i++) {             s[i] =  a ;             s[i + 1] =  b ;             i++;           }           int c = 97;           for (int i = n - k + 1; i <= n; i++) {             s[i] = c;             c++;           }         }       }       for (int i = 1; i <= n; i++) printf( %c , s[i]);       cout << endl;     }     return 0;   }   