import itertools
n=int(input())
a=list(map(int,input().split()))
b=list(map(int,input().split()))
l=[i for i in range(n)]
l2=list(itertools.permutations(l))
ans=0
for i in range(len(l2)):
  for j in range(len(l2)):
    ct=0
    for k in range(n):
      if a[l2[i][k]]>b[l2[j][k]]:
        ct+=1
      else:
        ct-=1
    if ct>0:
      ans+=1
print(ans/(len(l2)**2))