#include<iostream>
#include<string>
#include<algorithm>
#include<map>
#include<set>
#include<utility>
#include<vector>
#include<cmath>
#include<cstdio>
#define loop(i,a,b) for(int i=a;i<b;i++) 
#define rep(i,a) loop(i,0,a)
#define pb push_back
#define mp make_pair
#define it ::iterator
#define all(in) in.begin(),in.end()
const double PI=acos(-1);
const double ESP=1e-10;
using namespace std;
int main(){
  int n;
  cin>>n;
  vector<vector<int> >in(n+1,vector<int>(n+1));
  rep(i,n)rep(j,n){
    int d;cin>>d;
    rep(k,i+1)rep(l,j+1)in[k][l]+=d;
  }
  //rep(i,n){
  //  rep(j,n)printf("%2d",in[i][j]);//cout<<" "<<in[i][j];
  // cout<<endl;}
  int maxi=-1*1e9;
  rep(i,n)rep(j,n)loop(k,i,n)loop(l,j,n)
    maxi=max(maxi,in[i][j]+in[k+1][l+1]-in[k+1][j]-in[i][l+1]);
  cout<<maxi<<endl;
}