#include <bits/stdc++.h>
using namespace std;
int n, k;
string s, t;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cin >> n >> k >> s;
  for (int i = 0; i < n; i++) {
    if (k == 0)
      t += s[i];
    else {
      if (k < max(s[i] - 'a', 25 - (s[i] - 'a'))) {
        if (s[i] - 'a' > k)
          t += s[i] - k;
        else
          t += s[i] + k;
        k = 0;
      } else {
        if (s[i] - 'a' > 25 - (s[i] - 'a'))
          t += 'a';
        else
          t += 'z';
        k -= max(s[i] - 'a', 25 - (s[i] - 'a'));
      }
    }
  }
  if (k != 0)
    cout << -1 << '\n';
  else
    cout << t << '\n';
  return 0;
}
