def solve(M, S):
    DP = [[0] * (M + 1) for i in range(len(S))]
    for i in range(len(S)):
        DP[i][0] = 1.0

    for j in range(1, M + 1):
        step = 2 ** j
        for i in range(len(S)):
            l = (i // step) * step
            r = l + step
            if i - l >= r - i:
                r = (l + r) // 2
            else:
                l = (l + r) // 2
            DP[i][j] = 0.0
            for k in range(l, r):
                DP[i][j] += S[i] / (S[i] + S[k]) * DP[k][j - 1]
            DP[i][j] *= DP[i][j - 1]
    return DP[0][M]


def main():
    M = int(input())
    n = 2 ** M
    S = [int(input()) ** 2 for i in range(n)]

    print(solve(M, S))


if __name__ == '__main__':
    main()
# 解説をちら見してから考えたやつ