#include <iostream>
#include <cstdio>
#include <queue>
#include <stack>
#include <vector>
#include <algorithm>
#include <string>
#include <cstring>
#include <cmath>
#include <complex>
#include <map>
#include <climits>
#include <sstream>
using namespace std;

#define reep(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i,n) reep((i),0,(n))
#define ALL(v) (v).begin(),(v).end()
#define PB push_back
#define EPS 1e-8
#define F first
#define S second
#define mkp make_pair

static const double PI=6*asin(0.5);
typedef long long ll;
typedef complex<double> CP;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<int> vint;
static const int INF=1<<24;

template <class T>
void initvv(vector<vector<T> > &v,int a,int b, const T  &t = T()){
	v.assign(a,vector<T>(b,t));
}

//v.erase(unique(v.begin(),v.end()),v.end());


int main(){
	int n,k;
	while(cin>>n>>k,n||k){
		vint v(n);
		rep(i,n){
			cin>>v[i];
		}
		int MAX=0;
		rep(i,n-k+1){
			int ss=1;
			// cout<<"k "<<k<<endl;
			rep(j,k){
				ss*=v[j+i];
				// cout<<j<<" "<<v[j]<<endl;
			}
			// cout<<ss<<endl;
			MAX=max(MAX,ss);
		}
		int M=0;
		rep(i,n){
			rep(j,n){
				swap(v[i],v[j]);
				// int ss=1;
				rep(x,n-k+1){
					int ss=1;
					rep(y,k){
						ss*=v[y+x];
					}
					M=max(M,ss);
				}
				swap(v[i],v[j]);
			}
		}
		// cout<<M<<" "<<MAX<<endl;
		if(M<MAX){
			cout<<"NO GAME"<<endl;
		}
		else{
			cout<<M-MAX<<endl;
		}
	}
}