#include <bits/stdc++.h>
using namespace std;
char s[3 * 100010];
int main() {
  int n, k;
  scanf("%d%d%s", &n, &k, s);
  for (int i = 0; i < n && k > 0; i++) {
    int x = min(k, max(s[i] - 'a', 'z' - s[i]));
    k -= x;
    s[i] += (s[i] + x > 'z') ? -x : x;
  }
  printf(k == 0 ? s : "-1");
}
