#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<cassert>
#include<iostream>
#include<sstream>
#include<string>
#include<vector>
#include<queue>
#include<set>
#include<map>
#include<utility>
#include<numeric>
#include<algorithm>
#include<bitset>
#include<complex>
#include<stack>

using namespace std;

typedef long long Int;
typedef vector<int> vint;
typedef pair<int,int> pint;
typedef vector<string> vstring;
typedef vector<pint> vpint;
typedef stringstream SS;

struct Edge{int to,from,cost;};

#ifdef DEBUG
#define debug cout
#else
SS ss;
#define debug ss
#endif

template<class T> void chmin(T &t, T f) { if (t > f) t = f; }
template<class T> void chmax(T &t, T f) { if (t < f) t = f; }
int in() { int x; scanf("%d", &x); return x; }

#define rep(i,n) for(int i=0;i<(n);++i)
#define repn(i,m,n) for(int i=(m);i<=(n);++i)
#define repd(i,n) for(int i=(n)-1;i>=0;--i)
#define repnd(i,m,n) for(int i=(n);i>=(m);--i)
#define rep0(i,n) for(i=0;i<(n);++i)
#define repn0(i,m,n) for(i=(m);i<=(n);++i)
#define repd0(i,n) for(i=(n)-1;i>=0;--i)
#define repnd0(i,m,n) for(i=(n);i>=(m);--i)
#define all(n) n.begin(),n.end()
#define sz(n) ((int)(n).size())
#define IL for(;;)
#define MP make_pair
#define PB push_back
#define X second
#define Y first
#define PUTLINE debug<<"LINE:"<<__LINE__<<endl;

const int INF = 2147483647/3;
const double EPS = 1e-10;
const double PI = acos(-1.0);

const int dx[]={1,-1,0,0,1,-1,1,-1,0};
const int dy[]={0,0,1,-1,1,-1,-1,1,0};

int a[110];

int main() {
	int n,k;
	IL{
		cin>>n>>k;
		if(n==0&&k==0)break;
		rep(i,n)cin>>a[i];
		int mx=0;
		rep(i,n-k+1){
			int m=1;
			rep(j,k){
				m*=a[i+j];
			}
//cout<<i<<" "<<m<<endl;
			chmax(mx,m);
		}
		int mm=0;
		rep(i,n)rep(c,n)if(i!=c){
			swap(a[i],a[c]);
			rep(b,n-k+1){
				int m=1;
				rep(j,k){
					m*=a[b+j];
				}
				chmax(mm,m);
			}
			swap(a[i],a[c]);
		}
		if(mm<mx){
			cout<<"NO GAME"<<endl;
		}else{
			cout<<mm-mx<<endl;
		}
	}
	return 0;
}