#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m;
  string s;
  scanf("%d%d", &n, &m);
  cin >> s;
  int i = 0;
  while (m) {
    if (s[i] <= 'm') {
      if (('z' - s[i]) <= m) {
        m -= ('z' - s[i]);
        s[i] = 'z';
      } else {
        s[i] = (char)(s[i] + m);
        m = 0;
      }
    } else {
      if ((s[i] - 'a') <= m) {
        m -= (s[i] - 'a');
        s[i] = 'a';
      } else {
        s[i] = (char)(s[i] - m);
        m = 0;
      }
    }
    i++;
    if (i == n) break;
  }
  if (m == 0)
    cout << s;
  else
    printf("-1\n");
  return 0;
}
