#include <bits/stdc++.h>
using namespace std;
string s;
int n, k, cal;
string solve() {
  for (int i = 0; i < s.size(); i++) {
    int m4x = min(s[i] + k, (int)'z');
    int m1n = max(s[i] - k, (int)'a');
    if (s[i] - m1n >= m4x - s[i]) {
      k -= s[i] - m1n;
      s[i] = m1n;
    } else {
      k -= m4x - s[i];
      s[i] = m4x;
    }
  }
  if (k == 0) return s;
  return "-1";
}
int main() {
  cin >> n >> k >> s;
  cout << solve();
}
