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


def fanc(pa, pb, A, B):
    a = b = 0
    for _ in range(len(A)):
        i = random.randrange(len(A))
        if random.random() <= pa:
            i, va = min(enumerate(A), key=lambda x: x[1])
        else:
            va = A[i]
        del A[i]

        i = random.randrange(len(B))
        if random.random() <= pb:
            i, vb = min(enumerate(B), key=lambda x: x[1])
        else:
            vb = B[i]
        del B[i]

        if va > vb:
            a += va+vb
        else:
            b += va+vb
    if a > b:
        return 1
    else:
        return 0


def main():
    [n, pa, pb] = map(float, input().split())
    A = list(map(int, input().split()))
    B = list(map(int, input().split()))
    cnt, check = 0, 160000
    for _ in range(check):
        cnt += fanc(pa, pb, list(A), list(B))

    print(cnt/check)


if __name__ == '__main__':
    main()