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