#include <bits/stdc++.h>
#define ll long long
using namespace std;
ll a[201][201],b[201][201];
ll maxn,t;
ll m,n;
int main()
{
	freopen("long.in","r",stdin);
	freopen("long.out","w",stdout);
	scanf("%lld%lld",&n,&m);
	for (ll i=1;i<=n;i++)
	{
		for (ll j=1;j<=m;j++)
		{
			scanf("%lld",&a[i][j]);
			b[i][j]=b[i][j-1]+b[i-1][j]-b[i-1][j-1]+a[i][j];
		}
	}
	for (ll i=1;i<=n;i++) 
	{
		for (ll j=1;j<=m;j++) 
		{
			for (ll x=i;x<=n;x++)
			{
				for (ll y=j;y<=m;y++)
				{
					if (b[x][y]-b[x][j-1]-b[i-1][y]+b[i-1][j-1]>0)
					{
						t=(x-i+1)*(y-j+1);
						if (t>=maxn) maxn=t;
					}
				}
				
			}
		}
		
	}
	printf("%lld",maxn);
	return 0;
}