#include <bits/stdc++.h>
using namespace std;
const int N = 26;
int n, k;
string s, s1 = "";
int main() {
  scanf("%d%d", &n, &k);
  cin >> s;
  for (int i = 0; i < n; ++i) {
    int x = s[i] - 'a' + k, y = s[i] - 'a' - k;
    if (x > 25) x = 25;
    if (y < 0) y = 0;
    if (abs(s[i] - 'a' - x) >= abs(s[i] - 'a' - y)) {
      s1 += x + 'a';
      k -= abs(s[i] - 'a' - x);
    } else {
      s1 += y + 'a';
      k -= abs(s[i] - 'a' - y);
    }
  }
  if (k > 0)
    cout << -1;
  else
    cout << s1;
}
