N = int(input())
A = [-1] + list(map(int, input().split()))
M = 18
inf = 1 << 60
dp = [[-(10**18)] * 50 for i in range(1 << 18)]
for i in range(N, 0, -1):
    l = 2 * i
    r = 2 * i + 1
    for j in range(-M, M):
        dp[i][j] = max(0, dp[l][j + 1], dp[r][j + 1], dp[l][j - 1] + dp[r][j + 1], dp[l][j + 1] + dp[r][j - 1]) + A[i] * j
print(dp[1][0])