#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  int n, k, cnt;
  cin >> n >> k >> s;
  long long ans = 0;
  for (int i = 0; i < n; i++) {
    cnt = min(25, k);
    if (s[i] - 'a' >= 'z' - s[i]) {
      if (cnt < s[i] - 'a') {
        s[i] -= cnt;
        k -= cnt;
      } else {
        k -= s[i] - 'a';
        s[i] = 'a';
      }
    } else {
      if (cnt < 'z' - s[i]) {
        s[i] += cnt;
        k -= cnt;
      } else {
        k -= 'z' - s[i];
        s[i] = 'z';
      }
    }
    if (cnt = 0) break;
  }
  if (k)
    cout << -1 << endl;
  else {
    cout << s << endl;
  }
}
