#include <bits/stdc++.h>
using namespace std;
const long long N = 1005;
int32_t main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  long long n, k;
  string s;
  cin >> n >> k >> s;
  for (long long i = 0; i < n; i++) {
    char best = s[i];
    long long mx_dist = 0;
    for (char maybe = 'a'; maybe <= 'z'; maybe++) {
      long long d = abs(maybe - s[i]);
      if (d > mx_dist && d <= k) {
        best = maybe;
        mx_dist = d;
      }
    }
    k -= mx_dist;
    s[i] = best;
  }
  if (k > 0)
    cout << -1;
  else
    cout << s << "\n";
  return 0;
}
