#include <stdio.h>

#define LEN 101
int main(void)
{
	int a[LEN][LEN];
	int n,i,j;
	scanf("%d",&n);
	for (i = 0;i < n;i++)
	{
		for (j = 0; j <= i;j++)
		{
			scanf("%d",&a[i][j]);
		}
	}
	for (i = n - 2;i >= 0;i--)
	{
		for (j = 0;j <= i;j++)
		{
			a[i][j] += (a[i+1][j] > a[i+1][j+1] ? a[i+1][j] : a[i+1][j+1]);
		}
	}
	printf("%d\n",a[0][0]);
	return 0;
}