#include <bits/stdc++.h>
using namespace std;
void solve() {
  long long n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  string ss = s;
  for (long long i = 0; i < n && k > 0; ++i) {
    if (s[i] - 'a' > 'z' - s[i]) {
      long long x = min((long long)s[i] - 'a', k);
      s[i] = s[i] - x;
      k -= x;
    } else {
      long long x = min((long long)'z' - s[i], k);
      s[i] = s[i] + x;
      k -= x;
    }
  }
  if (k == 0) {
    cout << s << '\n';
  } else {
    cout << -1 << '\n';
  }
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  solve();
  return 0;
}
