#include <bits/stdc++.h>
using namespace std;
string s, s1;
int main() {
  int n, k;
  cin >> n >> k;
  cin >> s;
  for (int i = 0; i < s.size(); i++) {
    int dis1 = 'z' - s[i];
    int dis2 = s[i] - 'a';
    if (dis1 > dis2) {
      int ddd = min(dis1, k);
      k -= ddd;
      s1 += s[i] + ddd;
    } else {
      int ddd = min(dis2, k);
      k -= ddd;
      s1 += s[i] - ddd;
    }
  }
  if (k)
    return puts("-1");
  else
    cout << s1 << endl;
}
