#include <bits/stdc++.h>
char alph[] = "abcdefghijklmnopqrstuvwxyz";
int index(char c) { return (int)c - 97; }
int main() {
  int n, k;
  scanf("%d %d", &n, &k);
  char str[n + 3];
  scanf("%s", str);
  int i = 0;
  while (k > 0 && str[i] != '\0') {
    char c = str[i];
    if (index(c) < 13) {
      if (k <= 25 - index(c)) {
        str[i] = alph[index(c) + k];
        k = 0;
      } else {
        k -= 25 - index(c);
        str[i] = 'z';
      }
    } else {
      if (k <= index(c)) {
        str[i] = alph[index(c) - k];
        k = 0;
      } else {
        k -= index(c);
        str[i] = 'a';
      }
    }
    i++;
  }
  if (k > 0) {
    printf("-1\n");
    return 0;
  } else {
    printf("%s\n", str);
    return 0;
  }
}
