M = int(input())
S = [int(input()) for i in range(1<<M)]
dp = [[1]*(1<<M) for i in range(M+1)]
for i in range(M):
    for a in range(1<<M):
        win = dp[i][a]
        count = 0
        for b in range(1<<M):
            if a >> i+1 != b >> i+1:
                continue
            if a >> i & 1 == b >> i & 1:
                continue
            count += S[a]**2/(S[a]**2+S[b]**2)*dp[i][b]
        dp[i+1][a] = win*count
print(dp[-1][0])