#include<cstdio>
#include<iostream>
#include<cstring>
#define N 101
using namespace std;
int submatrix(int *a,int n){
	int i;
	int MAX=0;
	int sub=0;
	for(i=0;i<n;i++){
		if(sub>0){
			sub+=a[i];	
		}
		else{
			sub=a[i];
		}
		if(sub>MAX)
			MAX=sub;	
	}
	return MAX;
}
int n;
int matrix[N][N];
int a[N];
int maxsubmatrix=0;
int main(){
	int i,j,k;
	cin>>n;
	for(i=0;i<n;i++)
		for(j=0;j<n;j++)
			cin>>matrix[i][j];
	for(k=0;k<n;k++){
		memset(a,0,sizeof(a));
		for(i=k;i<n;i++){
			for(j=0;j<n;j++)
				a[j]+=matrix[i][j];
			maxsubmatrix=max(maxsubmatrix,submatrix(a,n));	
		}
	}
	cout<<maxsubmatrix<<endl;
	return 0;
}