#!/c/Python34/python
# coding: utf-8
import random


def simulate(n, pa, pb, A, B):
    a = b = 0
    for _ in range(n):
        ra, rb = random.random(), random.random()
        if ra < pa:
            va = A[-1]
            del A[-1]
        else:
            i = random.randrange(len(A))
            va = A[i]
            del A[i]
        if rb < pb:
            vb = B[-1]
            del B[-1]
        else:
            i = random.randrange(len(B))
            vb = B[i]
            del B[i]
        if va > vb:
            a += va+vb
        else:
            b += va+vb
    return a > b

def main():
    [n, pa, pb] = map(float, input().split())
    n = int(n)
    A = sorted(list(map(int, input().split())), reverse=True)
    B = sorted(list(map(int, input().split())), reverse=True)
    win, check = 0, 160000
    for _ in range(check):
        if simulate(n, pa, pb, list(A), list(B)):
            win += 1
    print(win/check)


if __name__ == '__main__':
    main()