#include <iostream>
#include <algorithm>
using namespace std;

int calc(int n, int k, int c[]) {
  int res = 0;
  int seki = 1;
  for(int i = 0; i < n; ++i) {
    if(i-k >= 0) seki /= c[i-k];
    seki *= c[i];
    if(i+1 >= k) res = max(res,seki);
  }
  return res;
}

int main() {
  int n, k, c[101];
  while(cin >> n >> k && (n|k)) {
    for(int i = 0; i < n; ++i) {
      cin >> c[i];
    }
    int C0 = calc(n,k,c);
    int C1 = 0;
    for(int i = 0; i < n; ++i) {
      for(int j = i+1; j < n; ++j) {
	swap(c[i],c[j]);
	C1 = max(C1, calc(n,k,c));
	swap(c[i],c[j]);
      }
    }
    if(C1-C0 < 0) cout << "NO GAME" << endl;
    else cout << C1-C0 << endl;
  }
  return 0;
}