m = int(input())
S = [float(input()) for _ in range(1 << m)]

def P(i, j):
    a = S[i] ** 2
    b = S[j] ** 2
    return a / (a + b)

dp = [1.0] * (1 << m)
for i in range(m):
    ndp = [0.0] * (1 << m)
    x = 0
    d = 1 << i
    while x < (1 << m):
        L = list(range(x, x + d))
        x += d
        R = list(range(x, x + d))
        x += d
        
        for l in L:
            for r in R:
                ndp[l] += dp[l] * dp[r] * P(l, r)
                ndp[r] += dp[l] * dp[r] * P(r, l)
    dp = ndp

print(dp[0])