#include<bits/stdc++.h>
using namespace std;
int n,a[200][200],m; 
int main(){
	scanf("%d",&n);
	for(int i=1;i<=n;i++){
		for(int j=1;j<=n;j++){
			if(i>=j){
				scanf("%d",&a[i][j]);
			}
		}
	}
	for(int i=n-1;i>=1;i--){
		for(int j=1;j<=i;j++){
			m=max(a[i+1][j],a[i+1][j+1]);
			a[i][j]=a[i][j]+m;
		}
	}
	cout<<a[1][1];
    return 0;
}


/**************************************************************
	Problem: 1216
	User: zhuangsongyu
	Language: C++
	Result: Accepted
	Time:16 ms
	Memory:2228 kb
****************************************************************/