#include <bits/stdc++.h>
using namespace ::std;
int main() {
  int n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  int i = 0, l = s.size();
  while (i < l && k != 0) {
    if (abs((int)s[i] - 'a') < abs((int)s[i] - 'z')) {
      if (abs((int)s[i] - 'z') >= k) {
        s[i] = (char)(s[i] + k);
        k = 0;
      } else {
        k -= abs((int)s[i] - 'z');
        s[i] = 'z';
      }
    } else {
      if (abs((int)s[i] - 'a') >= k) {
        s[i] = (char)(s[i] - k);
        k = 0;
      } else {
        k -= abs((int)s[i] - 'a');
        s[i] = 'a';
      }
    }
    i++;
  }
  if (k != 0)
    puts("-1");
  else
    cout << s << endl;
  return 0;
}
