#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  string ans = s;
  int x = k / n;
  int y = k % n;
  if (x > 25 || (x == 25 && y > 0)) {
    cout << -1 << endl;
    return 0;
  }
  for (int i = 0; i < n; i++) {
    if (k == 0) break;
    if ('z' - s[i] > s[i] - 'a') {
      if (k >= 'z' - s[i]) {
        ans[i] = 'z';
        k -= ('z' - s[i]);
      } else {
        ans[i] = s[i] + k;
        k = 0;
      }
    } else {
      if (k >= s[i] - 'a') {
        ans[i] = 'a';
        k -= (s[i] - 'a');
      } else {
        ans[i] = s[i] - k;
        k = 0;
      }
    }
  }
  if (k > 0) {
    cout << -1 << endl;
    return 0;
  }
  cout << ans << endl;
  return 0;
}
