#include <bits/stdc++.h>
char s[100001];
int main() {
  int n, k, max, f;
  scanf("%d%d", &n, &k);
  scanf("%s", s);
  max = 0;
  for (int i = 0; i < n; i++) {
    if (s[i] < 'n')
      max += 'z' - s[i];
    else
      max += s[i] - 'a';
  }
  if (max < k)
    printf("-1\n");
  else {
    f = 0;
    while (k > 0) {
      if (s[f] < 'n') {
        if (k >= 'z' - s[f]) {
          k -= 'z' - s[f];
          s[f] = 'z';
          f++;
        } else {
          s[f] += k;
          k = 0;
          f++;
        }
      } else {
        if (k >= s[f] - 'a') {
          k -= s[f] - 'a';
          s[f] = 'a';
          f++;
        } else {
          s[f] -= k;
          k = 0;
          f++;
        }
      }
    }
    for (int i = 0; i < n; i++) printf("%c", s[i]);
    printf("\n");
  }
  return 0;
}
