#include <bits/stdc++.h>
using namespace std;
char str[100003], ans[100003];
int main() {
  int n, k, tmp1, tmp2;
  scanf("%d%d", &n, &k);
  scanf("%s", str);
  for (int i = 0; i < n; i++) {
    tmp1 = 'z' - str[i];
    tmp2 = str[i] - 'a';
    if (max(tmp1, tmp2) > k && k > 0) {
      if (tmp1 >= k)
        ans[i] = str[i] + k;
      else
        ans[i] = str[i] - k;
      k -= max(tmp1, tmp2);
    } else if (max(tmp1, tmp2) <= k && k > 0) {
      if (tmp1 > tmp2) {
        ans[i] = 'z';
        k -= tmp1;
      } else {
        ans[i] = 'a';
        k -= tmp2;
      }
    } else
      ans[i] = str[i];
  }
  if (k <= 0) {
    for (int i = 0; i < n; i++) printf("%c", ans[i]);
  } else
    printf("-1");
  printf("\n");
}
