import sys
import numpy as np

nmax = int(1e6) + 10

n = int(input())
a = np.zeros((102, 102), dtype=np.int64)
f = np.zeros((102, 102), dtype=np.int64)

for i in range(1, n + 1):
    for j in range(1, i + 1):
        a[i][j] = int(input())

f[1][1] = a[1][1]
for i in range(2, n + 1):
    f[i][1] = f[i - 1][1] + a[i][1]

for i in range(2, n + 1):
    for j in range(2, i + 1):
        f[i][j] = max(f[i - 1][j - 1], f[i - 1][j]) + a[i][j]

res = 0
for i in range(1, n + 1):
    res = max(res, f[n][i])

print(res)