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


def simulate(n, pa, pb, A, B):
    a = b = 0
    a += 1
    for _ in range(n):
        ra, rb = random.random(), random.random()
        i, j = -1, -1
        if ra > pa and len(A) > 1:
            i = random.randrange(len(A)-1)
        if rb > pb and len(B) > 1:
            j = random.randrange(len(B)-1)
        if A[i] > B[j]:
            a += A[i] + B[j]
        else:
            b += A[i] + B[j]
        del A[i], B[j]
    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, 100000
    for _ in range(check):
        if simulate(n, pa, pb, A[:], B[:]):
            win += 1
    print(win/check)


if __name__ == '__main__':
    main()