#include <bits/stdc++.h>
using namespace std;
long long a[205][205],sum[205][205];
int main(){
    freopen("long.in","r",stdin);
    freopen("long.out","w",stdout);
	long long ans=0,z=0;
	int m,n;
	cin>>n>>m;
	for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            cin>>a[i][j]; 
            sum[i][j]=sum[i][j-1]+sum[i-1][j]-sum[i-1][j-1]+a[i][j];
        } 
    }
	for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){ 
            for(int x=i;x<=n;x++){
                for(int y=j;y<=m;y++){
		            if(sum[x][y]+sum[i-1][j-1]-sum[x][j-1]-sum[i-1][y]>0){
                        if((z=(long long)(x-i+1)*(y-j+1))>=ans){
                            ans=z;                
                        }
                    }
                }
            }
        }
    }
	cout<<ans<<endl; 
	fclose(stdin);
	fclose(stdout);
	return 0;
}