#include <bits/stdc++.h>
using namespace std;
ifstream fin("nr.in");
ofstream fout("nr.out");
int n,S[51][51],a,l=2,suma,maxim;
int main()
{
    cin >> n;
    for(int i=1;i<=n;i++)
    {
        for(int j=1;j<=n;j++)
        {
            cin >> a;
            S[i][j]=a+S[i-1][j]+S[i][j-1]-S[i-1][j-1];
        }
    }
    while(l<=n)
    {
        suma=0;
        for(int i=1;i<=n-l+1;i++)
        {
            for(int j=1;j<=n-l+1;j++)
            {
                suma=(S[i-1][j-1]+S[i+l-1][j+l-1]-S[i-1][j+l-1]-S[i+l-1][j-1])-(S[i][j]+S[i+l-2][j+l-2]-S[i][j+l-2]-S[i+l-2][j]);
                if(suma>maxim)
                    maxim=suma;
            }
        }
        l++;
    }
    if(maxim!=0)
        cout << maxim;
    else
        cout << S[1][1];
    return 0;
}