import math
import itertools
N=int(input())
A=list(map(int,input().split()))
B=list(map(int,input().split()))
t=math.factorial(N)**2
s=0
for x in itertools.permutations(A,N):
    for y in itertools.permutations(B,N):
        res=0
        for i in range(N):
            if(x[i]>y[i]):
                res+=1
        if(res>N-res):
            s+=1
print(s/t)