#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  int n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  for (int i = 0; i < n; i++) {
    if (abs('a' - s[i]) > abs('z' - s[i])) {
      int diff = min(s[i] - 'a', k);
      k -= diff;
      s[i] -= diff;
    } else {
      int diff = min('z' - s[i], k);
      k -= diff;
      s[i] += diff;
    }
  }
  if (k == 0)
    cout << s << endl;
  else
    cout << -1 << endl;
  return 0;
}
