#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  int i = 0;
  while (k != 0 && i < n) {
    int dist_a = abs(s[i] - 'a');
    int dist_z = abs(s[i] - 'z');
    if (dist_a >= dist_z) {
      if (dist_a >= k) {
        s[i] = (char)(s[i] - k);
        k = 0;
      } else {
        s[i] = 'a';
        k -= dist_a;
      }
    } else {
      if (dist_z >= k) {
        s[i] = (char)(s[i] + k);
        k = 0;
      } else {
        s[i] = 'z';
        k -= dist_z;
      }
    }
    i++;
  }
  if (k > 0)
    printf("-1\n");
  else
    cout << s;
  return 0;
}
