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()
B.sort()
dpA=[0]*(1<<N)
dpA[(1<<N)-1]=1
cardA=[[0]*N for i in range(N+1)]
for bit in range((1<<N)-1,-1,-1):
    cnt=sum(bit>>i&1 for i in range(N))
    for i in range(N):
        if bit>>i&1:
            break
    for j in range(N):
        if not bit>>j&1:
            continue
        if i==j:
            if cnt==1:
                dpA[bit^1<<j]+=dpA[bit]
                cardA[cnt][j]+=dpA[bit]
            else:
                dpA[bit^1<<j]+=dpA[bit]*PA
                cardA[cnt][j]+=dpA[bit]*PA
        else:
            dpA[bit^1<<j]+=dpA[bit]*(1-PA)/(cnt-1)
            cardA[cnt][j]+=dpA[bit]*(1-PA)/(cnt-1)
dpB=[0]*(1<<N)
dpB[(1<<N)-1]=1
cardB=[[0]*N for i in range(N+1)]
for bit in range((1<<N)-1,-1,-1):
    cnt=sum(bit>>i&1 for i in range(N))
    for i in range(N):
        if bit>>i&1:
            break
    for j in range(N):
        if not bit>>j&1:
            continue
        if i==j:
            if cnt==1:
                dpB[bit^1<<j]+=dpB[bit]
                cardB[cnt][j]+=dpB[bit]
            else:
                dpB[bit^1<<j]+=dpB[bit]*PB
                cardB[cnt][j]+=dpB[bit]*PB
        else:
            dpB[bit^1<<j]+=dpB[bit]*(1-PB)/(cnt-1)
            cardB[cnt][j]+=dpB[bit]*(1-PB)/(cnt-1)
ans=0
for cnt in range(1+N):
    for i in range(N):
        for j in range(N):
            if A[i]>B[j]:
                ans+=cardA[cnt][i]*cardB[cnt][j]*(A[i]+B[j])
print(ans)