#include <iostream>
#include <cstdio>
using namespace std;
const int N = 505;
int n, arr[N][N];
int main()
{
scanf("%d", &n);
for (int i = 1; i <= n; ++i)
for (int j = 1; j <= i; ++j)
scanf("%d", &arr[i][j]);
for (int i = n-1; i >= 1; --i)
for (int j = 1; j <= i; ++j)
arr[i][j] += max(arr[i+1][j], arr[i+1][j+1]);
printf("%d", arr[1][1]);
return 0;
}