#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int n, k, j;
  scanf("%d%d", &n, &k);
  char str[n + 5], out[n + 5];
  scanf("%s", &str);
  int ans = 0;
  for (int i = 0; i < n; i++) {
    if (str[i] - 'a' > abs(str[i] - 'z')) {
      ans += str[i] - 'a';
      out[i] = 'a';
    } else {
      ans = ans + abs(str[i] - 'z');
      out[i] = 'z';
    }
  }
  if (k > ans)
    puts("-1\n");
  else {
    int num;
    bool f = 0;
    for (int i = 0; i < n; i++) {
      num = abs(str[i] - out[i]);
      if (k > num)
        k -= num;
      else if (k == 0) {
        f = 1;
        j = i;
        break;
      } else {
        if (out[i] == 'z')
          out[i] = str[i] + k;
        else
          out[i] = str[i] - k;
        k = 0;
      }
    }
    if (f == 1) {
      for (int i = j; i < n; i++) {
        out[i] = str[i];
      }
    }
    for (int i = 0; i < n; i++) {
      printf("%c", out[i]);
    }
    printf("\n");
  }
  return 0;
}
