#include<cstdio>
#include<iostream>
#include<algorithm>
using namespace std;
const int MAX=1010;
int a[MAX][MAX];
int n;
int main(){
cin>>n;
for (int i=1;i<=n;i++)
for (int j=1;j<=i;j++)
cin>>a[i][j];
for (int i=n-1;i>=1;i--){
for (int j=1;j<=i;j++)
a[i][j]+=max(a[i+1][j+1],a[i+1][j]);
}
cout<<a[1][1]<<endl;
return 0;
}
1.摘花生
2.最低通行费
3.方格取数