/*

 ID: Starry21

 LANG: C++

 TASK: ariprog

 */

 #include<iostream>

 #include<string>

 #include<cstdio>

 #include<cstring>

 #include<vector>

 #include<algorithm>

 using namespace std;

 #define N 1005

 #define ll long long

 #define INF 0x3f3f3f3f

 int a[N][N],dp[N][N];

 int n;

 int main()

 {

     //freopen("ariprog.in","r",stdin);

     //freopen("ariprog.out","w",stdout);

     scanf("%d",&n);

     for(int i=;i<=n;i++)

         for(int j=;j<=i;j++)

         {

             scanf("%d",&a[i][j]);

             dp[i][j]=a[i][j];

         }

     for(int i=n-;i>=;i--)

         for(int j=;j<=i;j++)

             dp[i][j]=max(dp[i+][j],dp[i+][j+])+a[i][j];

     printf("%d\n",dp[][]);

     return ;

 }