#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint1000000007;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000000000000000

int main(){
	
	int N;
	cin>>N;
	
	vector<int> a(N),b(N);
	rep(i,N)cin>>a[i];
	rep(i,N)cin>>b[i];
	
	sort(a.begin(),a.end());
	double ans = 0.0;
	do{
		int w = 0,l = 0;
		rep(i,N){
			if(a[i]>b[i])w++;
			else l++;
		}
		if(w>l){
			ans += 1.0;
		}
	}
	while(next_permutation(a.begin(),a.end()));
	
	for(int i=1;i<=N;i++)ans /= i;
	
	cout<<fixed<<setprecision(10)<<ans<<endl;
	
	return 0;
}