#include <bits/stdc++.h>
using namespace std;
int n, k;
char s[100005];
int main() {
  scanf("%d %d\n", &n, &k);
  scanf("%s", s);
  int sz = strlen(s);
  for (int i = 0; i < sz and k; i++) {
    int a = min(25 - s[i] + 'a', k);
    int b = min(s[i] - 'a', k);
    if (a >= b) {
      k -= a;
      s[i] = s[i] + a;
    } else {
      k -= b;
      s[i] = s[i] - b;
    }
  }
  if (k)
    puts("-1");
  else
    printf("%s\n", s);
  return 0;
}
