#include <bits/stdc++.h>
using namespace std;
const int maxn = 3e5;
char s[maxn], t[maxn];
int n, k, i, j;
int main() {
  scanf("%d%d", &n, &k);
  scanf("%s", s + 1);
  for (i = 1; i <= n; i++) {
    t[i] = s[i];
    if (!k) continue;
    if (s[i] + k <= 'z') {
      t[i] = s[i] + k;
      k = 0;
    } else if (s[i] - k >= 'a') {
      t[i] = s[i] - k;
      k = 0;
    } else if ('z' - s[i] > s[i] - 'a')
      k -= 'z' - s[i], t[i] = 'z';
    else
      k -= s[i] - 'a', t[i] = 'a';
  }
  if (k == 0)
    printf("%s", t + 1);
  else
    printf("-1");
}
