#include<iostream>
using namespace std;
int s[1030][1030],a[1030][1030],n,maxn=-0x7fffffff;
int	main(){
	cin>>n;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            cin>>a[i][j];
            s[i][j]=s[i-1][j]+s[i][j-1]-s[i-1][j-1]+a[i][j];
        }
    }
    for(int x1=1;x1<=n;x1++){
        for(int y1=1;y1<=n;y1++){
            for(int x2=1;x2<=n;x2++){
                for(int y2=1;y2<=n;y2++){
                    maxn=max(maxn,s[x2][y2]-s[x1-1][y2]-s[x2][y1-1]+s[x1-1][y1-1]);
                }
            }
        }
    }
    cout<<maxn;
}