import sys
input = sys.stdin.readline

def win(si, sj):
    return si * si / (si * si + sj * sj)


M = int(input())
N = 1 << M
S = [int(input()) for _ in range(N)]

dp = [1] * N
op = [[i] for i in range(N)]
for i in range(M):
    dp_nxt = [0] * N
    for x in range(N):
        P = 0.
        opponent = op[x].copy()
        for y in opponent:
            y ^= (1 << i)
            P += win(S[x], S[y]) * dp[y]
            op[x].append(y)
        dp_nxt[x] = dp[x] * P
    dp = dp_nxt

print("{:.9f}".format(dp[0]))