#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  for (long long int i = 0; i < n && k; i++) {
    if (k >= max(abs('a' - s[i]), abs('z' - s[i]))) {
      k -= max(abs('a' - s[i]), abs('z' - s[i]));
      if (abs('a' - s[i]) > abs('z' - s[i]))
        s[i] = 'a';
      else
        s[i] = 'z';
    } else {
      if ('a' <= (s[i] - k))
        s[i] = (char)(s[i] - k);
      else
        s[i] = (char)(s[i] + k);
      k = 0;
    }
  }
  if (k == 0)
    cout << s;
  else
    cout << -1;
}
