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