#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k, i;
  string s;
  cin >> n >> k;
  cin >> s;
  for (i = 0; i < s.size(); i++) {
    int a = s[i] - 'a';
    int b = 'z' - s[i];
    int maxi = b, mini = a;
    char maxi_char = 'z';
    char mini_char = 'a';
    if (b < a) {
      swap(maxi, mini);
      swap(maxi_char, mini_char);
    }
    if (k >= maxi) {
      s[i] = maxi_char;
      k -= maxi;
    } else {
      if (maxi_char == 'a') {
        s[i] -= k;
      } else {
        s[i] += k;
      }
      k = 0;
      break;
    }
  }
  if (k == 0)
    cout << s << endl;
  else
    cout << "-1" << endl;
}
