#include <bits/stdc++.h>
using namespace std;
int main(){
	int n;	cin>>n;
	vector<int> a(n),b(n);
	for(int i=0;i<n;i++)	cin>>a[i];
	for(int i=0;i<n;i++)	cin>>b[i];
	sort(a.begin(),a.end());
	int win=0;
	do{
		sort(b.begin(),b.end());
		do{
			int cnt=0;
			for(int i=0;i<n;i++){
				if(a[i]>b[i])	cnt++;
			}
			if(cnt>n-cnt)	win++;
		}while(next_permutation(b.begin(),b.end()));
	}while(next_permutation(a.begin(),a.end()));
	int inv=1;
	for(int i=2;i<=n;i++)	inv*=i;
	cout<<(double)win/inv/inv<<endl;
	return 0;
}