def get(a,n,p):
    res = [[0.0]*n for _ in range(n)]
    N = 1<<n
    dp = [0.0]*N
    dp[0] = 1.0
    for mask in range(N-1):
        find = 0
        s = size[mask]
        if s==n-1:
            i = ((N-1)^mask).bit_length()-1
            res[s][i] += dp[mask]
            continue
        np = (1-p)/(n-s-1)
        for i in range(n):
            if mask>>i&1 == 0:
                if not find:
                    find = 1
                    dp[mask|(1<<i)] += dp[mask]*p
                    res[s][i] += dp[mask]*p
                else:
                    dp[mask|(1<<i)] += dp[mask]*np
                    res[s][i] += dp[mask]*np
    return res

n,pa,pb = input().split()
n = int(n)
pa,pb = float(pa), float(pb)
*a, = map(int,input().split())
*b, = map(int,input().split())
a.sort()
b.sort()
size = [0]*(1<<n)
for i in range(n):
    for j in range(1<<i):
        size[j+(1<<i)] = size[j] + 1

ra = get(a,n,pa)
rb = get(b,n,pb)
ans = 0
for s in range(n):
    for i,ai in enumerate(a):
        for j,bj in enumerate(b):
            if ai > bj:
                ans += ra[s][i]*rb[s][j]*(ai+bj)
print(ans)