#include <bits/stdc++.h>
using namespace std;
int n, k;
char s[100005];
int main() {
  char t;
  scanf("%d%d", &n, &k);
  scanf("%s", s);
  for (int i = 0; s[i]; i++) {
    if (s[i] > 'm') {
      t = 'a';
    } else {
      t = 'z';
    }
    if (k > abs(s[i] - t)) {
      k -= abs(s[i] - t);
      s[i] = t;
    } else {
      if (s[i] + k >= 'a' && s[i] + k <= 'z')
        s[i] += k;
      else
        s[i] -= k;
      k = 0;
      break;
    }
  }
  if (k > 0) {
    printf("-1\n");
  } else {
    printf("%s\n", s);
  }
  return 0;
}
