#include <bits/stdc++.h>
#pragma GCC optimize(2)
using namespace std;
long long a[201][201],sum[201][201];
inline int read()
{
	int k=0,f=1;
    char c=getchar();
	for(;!isdigit(c);c=getchar()) if(c=='-') f=-1;
	for(;isdigit(c);c=getchar()) k=(k<<1)+(k<<3)+(c&15);
	return k*f;
}
int main(){
    freopen("long.in","r",stdin);
	freopen("long.out","w",stdout);
	long long ans=0,z=0;
	int m,n,i,j,x,y;
	cin>>n>>m;
	for (i=1;i<=n;i++){
	    for (j=1;j<=m;j++){
            a[i][j]=read(); 
             sum[i][j]=sum[i][j-1]+sum[i-1][j]-sum[i-1][j-1]+a[i][j];
        }
    }  
	for(i=1;i<=n;i++){
	    for(j=1;j<=m;j++){
	        for(x=i;x<=n;x++){
	            for(y=j;y<=m;y++){
	                if((!(sum[x][y]+sum[i-1][j-1]-sum[x][j-1]-sum[i-1][y]<=0))&&(z=(long long)(x-i+1)*(y-j+1))>=ans) {
                       ans=z;  
                    } 
                }
            }
        }
    }    
	cout<<ans<<endl; 
	return 0;
}