#include <bits/stdc++.h>
using namespace std;
int n, k;
char s[111111];
int main() {
  scanf("%d%d", &n, &k);
  scanf("%s", s);
  for (int i = 0; i < n; i++) {
    int det = min(k, max('z' - s[i], s[i] - 'a'));
    k -= det;
    if (s[i] - det >= 'a')
      s[i] -= det;
    else
      s[i] += det;
  }
  if (k)
    printf("-1\n");
  else
    printf("%s\n", s);
  return 0;
}
