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