n=int(input())
a=[[0 for i in range(n)] for j in range(n)]
for i in range(n):
    sr=input().split()
    for j in range(i+1):
        a[i][j]=int(sr[j])
for i in range(n-2,-1,-1):
    for j in range(i+1):
        a[i][j]=a[i][j]+max(a[i+1][j],a[i+1][j+1])
print(a[0][0])
/**************************************************************
	Problem: 1216
	User: admin
	Language: Python
	Result: Accepted
	Time:229 ms
	Memory:34612 kb
****************************************************************/