#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n, k, ind = 0;
  cin >> n >> k;
  string s, s1;
  cin >> s;
  if (25 * n < k) {
    cout << -1 << endl;
    return 0;
  }
  s1.resize(s.length());
  while (s.length() != 0) {
    int o = (int)s[0] - 97;
    if (o >= 12) {
      if (o < k) {
        s1[ind] = (char)97;
        s.erase(s.begin());
        k = k - o;
        ind = ind + 1;
      } else {
        s1[ind] = (char)(o - k + 97);
        s.erase(s.begin());
        k = 0;
        ind = ind + 1;
      }
    } else {
      if (25 - o < k) {
        s1[ind] = (char)122;
        s.erase(s.begin());
        k = k - 25 + o;
        ind = ind + 1;
      } else {
        s1[ind] = (char)(o + k + 97);
        s.erase(s.begin());
        k = 0;
        ind = ind + 1;
      }
    }
  }
  if (k != 0)
    cout << -1 << endl;
  else
    cout << s1 << endl;
  return 0;
}
