#include<bits/stdc++.h>
#define rep(i,n)for(int i=0;i<(n);i++)
using namespace std;

int c[100];
int main() {
	int n, k;
	while (scanf("%d%d", &n, &k), n) {
		rep(i, n)scanf("%d", &c[i]);
		int a = 0, b = 0;
		int r = 1;
		rep(i, n) {
			if (i - k >= 0)r /= c[i - k];
			r *= c[i];
			a = max(a, r);
		}
		rep(i, n)for (int j = i + 1; j < n; j++) {
			swap(c[i], c[j]);
			r = 1;
			rep(i, n) {
				if (i - k >= 0)r /= c[i - k];
				r *= c[i];
				b = max(b, r);
			}
			swap(c[i], c[j]);
		}
		if (b < a)puts("NO GAME");
		else printf("%d\n", b - a);
	}
}