#include <bits/stdc++.h>
using namespace std;
string second, t;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n, k;
  cin >> n >> k >> second;
  for (int i = 0; i < second.size(); i++) {
    char c;
    if (k >= 'z' - second[i] && k >= second[i] - 'a') {
      if (second[i] <= 'm') {
        t += 'z';
        k -= 'z';
        k += second[i];
      } else {
        t += 'a';
        k -= second[i];
        k += 'a';
      }
    } else {
      if (second[i] + k <= 'z') {
        t += second[i] + k;
      } else {
        t += second[i] - k;
      }
      k = 0;
    }
  }
  if (k > 0) {
    cout << -1;
    return 0;
  }
  cout << t;
  return 0;
}
