import io
import sys

sys.stdin = io.StringIO('''5
7
3 8
8 1 0
2 7 4 4
4 5 2 6 5''')

n = int(input())
nums = []
for i in range(n):
    nums.append(list(map(int, input().split())))

f = [[0] * (n + 1) for _ in range(n + 1)]
for i in range(n - 1, -1, -1):
    for j in range(i + 1):
        f[i][j] = max(f[i + 1][j], f[i + 1][j + 1]) + nums[i][j]

print(f[0][0])