#include<stdio.h>
#define max(a,b)	(a>b?a:b)
int a[110][110];
int main()
{
	int n;
	scanf("%d",&n);
	for(int i=1;i<=n;i++)
	for(int j=1;j<=i;j++)
	scanf("%d",&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],a[i+1][j+1])+a[i][j];
	printf("%d",a[1][1]);
	return 0;
}
/**************************************************************
	Problem: 1216
	User: admin
	Language: C
	Result: Accepted
	Time:21 ms
	Memory:1192 kb
****************************************************************/