import sys
input = sys.stdin.readline

M = int(input())
M2 = 1 << M
S = [0] * M2
for i in range(M2):
    S[i] = int(input())

pre = [1] * M2
for i in range(M):
    dp = [0] * M2
    for j in range(M2):
        for k in range(M2):
            if j >> (i + 1) != k >> (i + 1):
                continue
            if (j >> i) & 1 != (k >> i) & 1:
                dp[j] += S[j] ** 2/(S[j] ** 2 + S[k] ** 2) * pre[j] * pre[k]
    dp, pre = pre, dp

print(pre[0])