#include <bits/stdc++.h>
using namespace std;
long long n,m,a[210][210],sum[210][210];
int res;
int main () {
	freopen("long.in","r",stdin);
	freopen("long.out","w",stdout);
	ios::sync_with_stdio(0);
	cin.tie(0),cout.tie(0);
	cin >> n >> m;
	for (int i=1;i<=n;i++) {
		for (int j=1;j<=m;j++) {
			cin >> a[i][j];
		}
	}
	for (int i=1;i<=n;i++) {
		for (int j=1;j<=m;j++) {
			sum[i][j]=a[i][j]+sum[i-1][j]+sum[i][j-1]-sum[i-1][j-1];
		}
	}
	for (int i=1;i<=n;i++) {
		for (int j=1;j<=m;j++) {
			for (int k=i;k<=n;k++) {
				for (int t=j;t<=m;t++) {
					if (sum[k][t]-sum[i-1][t]-sum[k][j-1]+sum[i-1][j-1]>=0) {
						res=max(res,(k-i+1)*(t-j+1));
					}
				}
			}
		}
	}
	cout << res;
	return 0;
}