#include <bits/stdc++.h>
using namespace std;
long long n, m, x, y, z, w, k, t, ans, a[300100], b[300100];
string s, f;
int main() {
  ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
  cin >> n >> k >> s;
  for (int i = 0; i < n; i++) {
    x += max(s[i] - 'a', 'z' - s[i]);
  }
  if (k > x) return cout << -1, 0;
  for (int i = 0; i < n; i++) {
    if (k - max(s[i] - 'a', 'z' - s[i]) >= 0) {
      if (s[i] - 'a' > 'z' - s[i])
        cout << 'a';
      else
        cout << 'z';
      k -= max(s[i] - 'a', 'z' - s[i]);
    } else {
      char c;
      if (s[i] - 'a' > 'z' - s[i]) {
        c = s[i] - k;
        cout << c;
      } else {
        c = s[i] + k;
        cout << c;
      }
      k = 0;
    }
  }
  return 0;
}
