import math
import itertools
N=int(input())
A=list(map(int,input().split()))
B=list(map(int,input().split()))
A=list(itertools.permutations(A))
B=list(itertools.permutations(B))
t=math.factorial(N)
ans=0
for i in range(t):
    for j in range(t):
        a=A[i];b=B[j]
        tmp=0
        for k in range(N):
            if a[k]>b[k]:
                tmp+=1
        if tmp>N//2:
            ans+=1
        print(a,b,tmp)
print(ans/(t**2))