/*
入门级dp
dp必做
*/
#define LOCAL
#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>
#include<cstdlib>
#include<iomanip>
#include<string>
#include<algorithm>
#include<ctime>
#include<stack>
#include<queue>
#include<vector>
#define N 105
using namespace std;
int dp[N][N],a[N][N];
int main()
{
#ifdef LOCAL
       freopen("input.txt","r",stdin);
       freopen("output.txt","w",stdout);
#endif
 
	int i,j,len,max;
	memset(dp,0,sizeof(dp));
	memset(a,0,sizeof(a));
	cin>>len;
	for(i=1;i<=len;i++)
		for(j=1;j<=i;j++)
			cin>>a[i][j];
	for(i=1;i<=len;i++)
	{
		for(j=1;j<=i;j++)
		{
			if(j==1){dp[i][j]=dp[i-1][j]+a[i][j];}
			else if(i==j){dp[i][j]=dp[i-1][j-1]+a[i][j];}
			else dp[i][j]=a[i][j]+(dp[i-1][j]>dp[i-1][j-1]?dp[i-1][j]:dp[i-1][j-1]);
		}
	}
	max=dp[len][1];
	for(i=2;i<=len;i++)
		if(max<dp[len][i])
			 max=dp[len][i];
	cout<<max<<endl;
	return 0;
}