#include <bits/stdc++.h>
using namespace std;
int n, k, d, x;
string s, ans;
int main() {
  int i;
  cin >> n >> k >> s;
  for (i = 0; i < s.size(); i++) {
    if (s[i] <= 'm') {
      d = 'z' - s[i];
      x = min(d, k);
      ans += s[i] + x;
    } else {
      d = s[i] - 'a';
      x = min(d, k);
      ans += s[i] - x;
    }
    k -= x;
  }
  if (k == 0)
    cout << ans;
  else
    cout << -1;
  return 0;
}
