#include <bits/stdc++.h>
using namespace std;
int main() {
  char str[1000010], str2[100010];
  char ch;
  int i, j, k, l, m, n, sum = 0;
  cin >> n >> k;
  scanf("%s", str);
  for (i = 0; str[i]; i++) {
    l = str[i];
    int ma = 0;
    ch = str[i];
    for (j = 97; j <= 122; j++) {
      if (abs(l - j) > ma && sum + abs(l - j) <= k) {
        ch = j;
        ma = abs(l - j);
      }
    }
    sum = sum + ma;
    str2[i] = ch;
  }
  str2[i] = '\0';
  if (sum < k) {
    printf("-1");
    return 0;
  }
  printf("%s\n", str2);
}
