#include <iostream>
#include <fstream>
using namespace std;
bool ground[50][50];

int main()
{
    freopen("sticks.in","r",stdin);
    freopen("sticks.out","w",stdout);
    int n,br=0,max=0;
    cin>>n;
    for(int i=0;i<n;i++)
        for(int j=0;j<n;j++)
            cin>>ground[i][j];
    for(int i=0;i<n;i++)
        for(int j=0;j<n;j++)
            for(int i1=i;i1<n;i1++)
                for(int j1=j;j1<n;j1++)
                {
                    int broken=0;
                    for(int r=i;r<=i1;r++)
                    {
                        for(int c=j;c<=j1;c++)
                            if(ground[r][c]==0){broken=1;break;}
                            if(broken==1)break;
                    }
                    if(broken==0)
                    {
                        if((i1-i+1)*(j1-j+1)>max)max=(i1-i+1)*(j1-j+1);
                    }
                }
    cout<<max<<endl;
    return 0;
}