n = int(input())
assert 1 <= n <= 10**5
a = [0, *map(int, input().split())]
for i in a:
    assert 0 <= i <= 10**9

dp = [[0] * (n + 1) for i in range(37)]

for i in range(n, 0, -1):
    lg = i.bit_length() - 1
    for j in range(-lg, lg + 1, 2):
        cnt1 = 0
        cnt2 = 0
        if i * 2 <= n:
            cnt1 += max(0, dp[j + 1][i * 2])
            cnt2 += max(0, dp[j - 1][i * 2])
        if i * 2 + 1 <= n:
            cnt1 += max(0, dp[j - 1][i * 2 + 1])
            cnt2 += max(0, dp[j + 1][i * 2 + 1])
        dp[j][i] = a[i] * j + max(cnt1, cnt2)

print(dp[0][1])