#include <bits/stdc++.h>
using namespace std;
char enl = '\n';
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  string res;
  for (auto c : s) {
    int charpos = c;
    if (k > 0) {
      int sign = 1;
      int maxleft = c - 'a';
      int maxright = 'z' - c;
      if (maxleft > maxright) {
        charpos = 'a';
        sign = 1;
      } else {
        charpos = 'z';
        sign = -1;
      }
      k -= max(maxleft, maxright);
      if (k < 0) {
        charpos -= k * sign;
      }
    }
    char ca = charpos;
    res += ca;
  }
  if (k <= 0)
    cout << res << enl;
  else
    cout << -1 << enl;
  return 0;
}
