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