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