#include <bits/stdc++.h>
using namespace std;
char str[210000];
int vis[210000];
int main() {
  int n, k;
  while (scanf("%d %d", &n, &k) != EOF) {
    scanf("%s", str);
    for (int i = 0; i < n; i++) {
      if ('z' - str[i] > str[i] - 'a') {
        if (k >= 'z' - str[i]) {
          k -= ('z' - str[i]);
          str[i] += ('z' - str[i]);
        } else {
          str[i] += k;
          k = 0;
        }
      } else {
        if (k >= str[i] - 'a') {
          k -= (str[i] - 'a');
          str[i] -= (str[i] - 'a');
        } else {
          str[i] -= k;
          k = 0;
        }
      }
    }
    str[n] = '\0';
    if (k > 0)
      puts("-1");
    else
      puts(str);
  }
  return 0;
}
