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