#include <bits/stdc++.h>
using namespace std;
char s[100005];
int k;
int main() {
  int n;
  scanf("%d%d", &n, &k);
  scanf("%s", s);
  for (int i = 0; i < n; i++) {
    if (s[i] - 'a' > 'z' - s[i] && k >= s[i] - 'a')
      k -= s[i] - 'a', s[i] = 'a';
    else if (s[i] - 'a' <= 'z' - s[i] && k >= 'z' - s[i])
      k -= 'z' - s[i], s[i] = 'z';
    else if (s[i] + k > 'z')
      s[i] = s[i] - k, k = 0;
    else
      s[i] = s[i] + k, k = 0;
    if (!k) break;
  }
  if (k) return 0 * puts("-1");
  puts(s);
  return 0;
}
