#include <iostream>
using namespace std;
int a[51][51],n,s=-100;
int main()
{
    cin>>n;
    for(int i=1;i<=n;i++)for(int j=1;j<=n;j++){cin>>a[i][j];if(a[i][j]>s)s=a[i][j];a[i][j]=a[i][j]-a[i-1][j-1]+a[i-1][j]+a[i][j-1];}
    for(int i=1;i<=n;i++)for(int j=1;j<=n;j++)for(int l=min(i,j);l>1;l--)
    {
        int S=a[i][j]+a[i-l][j-l]-a[i][j-l]-a[i-l][j]+a[i-1][j-l+1]+a[i-l+1][j-1]-a[i-1][j-1]-a[i-l+1][j-l+1];
        if(S>s)s=S;
    }
    cout<<s;
}