#include<bits/stdc++.h>
using namespace std;
long long n,m,maxc = 0;
long long a[105][105];
bool pd(int xl,int y1,int x2,int y2){
	int al = 0,bl = 0;
	for(int i = xl;i <= x2;i++){
		for(int j = y1;j <= y2;j++){
			if(a[i][j] == 1) al++;
			else if(a[i][j] == 0) bl++;
		}
	}
	return (al == bl);
}
int main(){
	cin >> n >> m;
	for(int i = 1;i <= n;i++){
		for(int j = 1;j <= m;j++){
			cin >> a[i][j];
		}
	}
	for(long long i = 1;i <= n;i++){
		for(long long j = 1;j <= m;j++){
			for(long long l = i;l <= n;l++){
				for(long long k = j;k <= m;k++){
					if(pd(i,j,l,k)){
						maxc = max(maxc,(l - i + 1) * (k - j + 1));
					}
				}
			}
		} 
	}
	cout<<maxc;
	return 0;
}