#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  int n, k;
  string s;
  cin >> n >> k;
  cin >> s;
  if (k > s.size() * 25) {
    cout << "-1\n";
    return 0;
  }
  string out;
  for (char c : s) {
    c -= 'a';
    int mv;
    if (25 - c > c) {
      mv = min(25 - (int)c, k);
      c += mv;
    } else {
      mv = min((int)c, k);
      c -= mv;
    }
    out.push_back(c + 'a');
    k -= mv;
  }
  if (k > 0) {
    cout << "-1\n";
    return 0;
  }
  cout << out << '\n';
  return 0;
}
