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