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