#include <iostream>

#include <cstdio>

#include <stdlib.h>

#include <memory.h>

using namespace std;

int s[][],dp[],n,temp[];

int main()

{

    // freopen("in.txt","r",stdin);

    cin>>n;

    for(int i=;i<=n;i++)

        for(int j=;j<=n;j++)

            cin>>s[i][j];

    int maxx = ;

    for (int i=;i<=n;i++) //start from line i

    {

        memset(temp,,sizeof(temp));

        for (int j=i;j<=n;j++) //end at line j

        {

            for (int k=;k<=n;k++)

            {

                temp[k]+=s[j][k];

                if (temp[k]+dp[k-]>)

                dp[k]=temp[k]+dp[k-];

                else

                dp[k]=;

                if (maxx<dp[k])

                    maxx =dp[k];

            }

        }

     }

    cout << maxx << endl;

}