#include<iostream>
using namespace std;
int a[1005][1005],c[1005][1005];
int n,mmax;

int main(){
    cin>>n;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            cin>>a[i][j];
            if(j==1){
                c[i][j]=a[i][j]+c[i-1][j];
            }else{
                if(c[i-1][j]>c[i][j-1]){
                    c[i][j]=a[i][j]+c[i-1][j];
                }else{
                    c[i][j]=a[i][j]+c[i][j-1];
                }
            }
            if(c[i][j]>mmax){
                mmax=c[i][j];
            }
        }
    }
    cout<<mmax;
    return 0;
}