#include <iostream>
#include <sstream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <ctime>
#include <cstring>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <deque>
#include <map>
#include <set>
#include <bitset>
#include <numeric>
#include <utility>
#include <iomanip>
#include <algorithm>
#include <functional>
using namespace std;

typedef long long ll;
typedef vector<int> vint;
typedef vector<long long> vll;
typedef pair<int,int> pint;
typedef pair<long long, long long> pll;

#define MP make_pair
#define PB push_back
#define ALL(s) (s).begin(),(s).end()
#define EACH(i, s) for (__typeof__((s).begin()) i = (s).begin(); i != (s).end(); ++i)
#define COUT(x) cout << #x << " = " << (x) << " (L" << __LINE__ << ")" << endl

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<class T1, class T2> ostream& operator << (ostream &s, pair<T1,T2> P) 
{ return s << '<' << P.first << ", " << P.second << '>'; }
template<class T> ostream& operator << (ostream &s, vector<T> P) 
{ for (int i = 0; i < P.size(); ++i) { if (i > 0) { s << " "; } s << P[i]; } return s; }
template<class T1, class T2> ostream& operator << (ostream &s, map<T1,T2> P) 
{ EACH(it, P) { s << "<" << it->first << "->" << it->second << "> "; } return s; }

int n, k;
int c[120];

int score(int c[]) {
    int res = 1;
    for (int i = 0; i + k <= n; ++i) {
        int tmp = 1;
        for (int j = i; j < i+k; ++j) tmp *= c[j];
        chmax(res, tmp);
    }
    return res;
}

int main() {
    while (cin >> n >> k) {
        if (n == 0) break;
        for (int i = 0; i < n; ++i) cin >> c[i];
        int prev = score(c);
        int Max = -1;
        for (int i = 0; i < n; ++i) {
            for (int j = i+1; j < n; ++j) {
                swap(c[i], c[j]);
                int s = score(c);
                swap(c[i], c[j]);
                chmax(Max, s);
            }
        }
        int res = Max - prev;
        if (res >= 0) cout << res << endl;
        else puts("NO GAME");
    }
    return 0;
}
