// poj1050

#include<algorithm>

#include<iostream>

#include<cstdlib>

#include<cstring>

#include<cstdio>

#include<cmath>

#define LL long long

#define inf 2147483640

#define Pi 3.1415926535898

#define free(a) freopen(a".in","r",stdin),freopen(a".out","w",stdout);

using namespace std;

int n,a[1010][1010],sum[1010][1010];

int main() {

    scanf("%d",&n);

    for (int i=1;i<=n;i++)

        for (int j=1;j<=n;j++) scanf("%d",&a[i][j]),sum[i][j]=a[i][j]+sum[i][j-1];

    int ans=-inf;

    for (int i=1;i<=n;i++)

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

            int s=0;

            for (int k=1;k<=n;k++) {

                s+=sum[k][j]-sum[k][i-1];

                if (s<0) s=0;

                else ans=max(ans,s);

            }

        }

    printf("%d",ans);

    return 0;

}