#include <bits/stdc++.h>
using namespace std;
long long A[3 * 100005];
char s[3 * 100005], ans[100005];
int ABS(int num) {
  if (num < 0) return -num;
  return num;
}
int main() {
  int n, K;
  scanf("%d %d", &n, &K);
  scanf("%s", s);
  int N = strlen(s);
  long long cnt = 0;
  for (int i = 0; i < N; i++) {
    cnt = cnt + max(s[i] - 'a', 'z' - s[i]);
  }
  if (cnt < K) {
    printf("-1\n");
    return 0;
  }
  for (int i = 0; i < N; i++) ans[i] = s[i];
  for (int i = 0; i < N; i++) {
    int now = max(s[i] - 'a', 'z' - s[i]);
    if (now > K) {
      if ((s[i] - 'a') > ('z' - s[i])) {
        ans[i] = s[i] - K;
      } else {
        ans[i] = ans[i] + K;
      }
      break;
    }
    if ((s[i] - 'a') > ('z' - s[i]))
      ans[i] = 'a';
    else
      ans[i] = 'z';
    K = K - now;
  }
  ans[N] = 0;
  printf("%s\n", ans);
}
