#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cmath>
#include<cctype>
#include<math.h>
#include<string>
#include<string.h>
#include<stack>
#include<queue>
#include<vector>
#include<utility>
#include<set>
#include<map>
#include<stdlib.h>
#include<iomanip>

using namespace std;

#define ll long long
#define ld long double
#define EPS 0.0000000001
#define INF 1e9
#define LINF (ll)INF*INF
#define MOD 1000000007
#define rep(i,n) for(int i=0;i<(n);i++)
#define loop(i,a,n) for(int i=a;i<(n);i++)
#define all(in) in.begin(),in.end()
#define shosu(x) fixed<<setprecision(x)

#define int ll //!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

typedef vector<int> vi;
typedef vector<string> vs;
typedef pair<int,int> pii;
typedef vector<pii> vp;

int gcd(int a, int b){
    if(b==0) return a;
    return gcd(b,a%b);
}
int lcm(int a, int b){
    return a/gcd(a,b)*b;
}

int v[100][100];

int f(int a, int b, int c, int d){
    int ret = v[c][d];
    if(a)ret -= v[a-1][d];
    if(b)ret -= v[c][b-1];
    if(a&&b)ret += v[a-1][b-1];
    return ret;
}

signed main(void) {
    int n;
    cin >> n;
    rep(i,n)rep(j,n)cin >> v[i][j];
    rep(i,n)rep(j,n-1)v[i][j+1] += v[i][j];
    rep(j,n)rep(i,n-1)v[i+1][j] += v[i][j];
    int ans = 0;
    rep(i,n)rep(j,n)loop(k,i,n)loop(l,j,n){
        ans = max(ans, f(i,j,k,l));
    }
    cout << ans << endl;
}

