def read_data():
    N, Pa, Pb = input().split()
    N = int(N)
    Pa = float(Pa)
    Pb = float(Pb)
    A = list(map(int, input().split()))
    B = list(map(int, input().split()))
    A.sort(reverse=True)
    B.sort(reverse=True)
    return N, Pa, Pb, A, B

def solve(N, Pa, Pb, A, B):
    Nsim = 10**6
    Awin = 0
    for i in range(Nsim):
        if simulate(N, Pa, Pb, A[:], B[:]):
            Awin += 1
    return Awin / Nsim

import random
def simulate(N, Pa, Pb, A, B):
    scoreA = 0
    scoreB = 0
    for i in range(N-1, 0, -1):
        ra = random.random()
        rb = random.random()
        if ra < Pa:
            pa = A[-1]
            del A[-1]
        else:
            ia = random.randrange(0, i)
            pa = A[ia]
            del A[ia]
        if rb < Pb:
            pb = B[-1]
            del B[-1]
        else:
            ib = random.randrange(0, i)
            pb = B[ib]
            del B[ib]
        if pa > pb:
            scoreA += pa + pb
        elif pa < pb:
            scoreB += pa + pb
    pa = A[0]
    pb = B[0]
    if pa > pb:
        scoreA += pa + pb
    elif pa < pb:
        scoreB += pa + pb
    return scoreA > scoreB

N, Pa, Pb, A, B = read_data()
print(solve(N, Pa, Pb, A, B))