#include <bits/stdc++.h>
int main(void) {
  int n, k, c, cc, flag = 0, cnt = 1;
  int card[10];
  int i, j;
  scanf("%d %d", &n, &k);
  for (i = 0; i < n; i++) scanf("%d", &card[i]);
  while ((n != 0 && k != 0) && cnt <= 100) {
    cc = card[n - 1] * card[n - 2];
    c = cc;
    for (i = 0; i < n; i++) {
      for (j = 0; j < i; j++) {
        if (card[i] * card[j] >= c) {
          c = card[i] * card[j];
          flag = 1;
        }
      }
    }
    if (flag == 1)
      printf("%d\n", c - cc);
    else
      printf("NO GAME\n");
    scanf("%d %d", &n, &k);
    for (i = 0; i < n; i++) scanf("%d", &card[i]);
    cnt++;
  }
  return 0;
}
