n = int(input())
a = [[int(j) for j in input().split()] for i in range (n)]
for i in range(0, n - 1)[::-1]:
    for j in range(i + 1):
        a[i][j] += max(a[i + 1][j], a[i + 1][j + 1])
print(a[0][0])