#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  int n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  string res = "";
  for (int i = 0; i < n; i++) {
    if ((s[i] - 'a') >= ('z' - s[i])) {
      if ((s[i] - 'a') <= k) {
        k -= (s[i] - 'a');
        res += 'a';
      } else {
        res += (char)(s[i] - k);
        k = 0;
      }
    } else {
      if (('z' - s[i]) <= k) {
        k -= ('z' - s[i]);
        res += 'z';
      } else {
        res += (char)(s[i] + k);
        k = 0;
      }
    }
  }
  if (k != 0) {
    cout << -1;
  } else {
    cout << res;
  }
}
