#include<iostream>
using namespace std;
int a[15][15];
bool check(int x1, int y1, int x2, int y2)
{
	int x[2] = {0, 0};
	for (int i = x1; i <= x2; i++)
		for (int j = y1; j <= y2; j++)
			x[a[i][j]]++;
	return x[0] == x[1];
}
int main()
{
	int n, m;
	cin >> n >> m;
	for(int i = 1; i <= n; i++)
        for(int j = 1; j <= m; j++)
            cin >> a[i][j];
	int ans = 0;
	for (int i = 1; i <= n; i++)
    {
		for (int j = 1; j <= m; j++)
		{
			for (int ii = i; ii <= n; ii++)
            {
				for (int jj = j; jj <= m; jj++)
                {
					if (check(i, j, ii, jj))
						ans = max(ans, (ii - i + 1) * (jj - j + 1));
				}
			}
		}
	}
	cout << ans << endl;
	return 0;
}