#include <bits/stdc++.h>
using namespace std;
int Max(int n, int K, int c[]) {
  int k, l, CK, M = 0;
  for (k = 0; k < n - K + 1; k++) {
    CK = 1;
    for (l = k; l < k + K; l++) {
      CK *= c[l];
    }
    if (CK > M) M = CK;
  }
  cout << "M:" << M << endl;
  return M;
}
int main() {
  int n, K, M1, M2, tmp, cnt = 0;
  int i, j;
  int c[100];
  while (cnt < 100) {
    cnt++;
    cin >> n >> K;
    if (n == 0 && K == 0) break;
    for (i = 0; i < n; i++) cin >> c[i];
    M1 = 0;
    M2 = 0;
    if (M1 < Max(n, K, c)) M1 = Max(n, K, c);
    for (i = 0; i < n - 1; i++) {
      for (j = i + 1; j < n; j++) {
        tmp = c[i];
        c[i] = c[j];
        c[j] = tmp;
        if (M2 < Max(n, K, c)) M2 = Max(n, K, c);
        tmp = c[i];
        c[i] = c[j];
        c[j] = tmp;
      }
    }
    if (M1 <= M2)
      cout << M2 - M1 << endl;
    else
      cout << "NO GAME" << endl;
  }
  return 0;
}
