#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define MOD 1000000007
#define INF 1e9
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define all(x) (x).begin(),(x).end()
template<typename T> using min_priority_queue = priority_queue<T, vector<T>, greater<T>>;

int main(){
	int N;
	cin>>N;
	vector<int> A(N);
	vector<int> B(N);
	rep(i,N) cin>>A[i];
	rep(i,N) cin>>B[i];

	vector<int> NA(N),NB(N);
	rep(i,N) NA[i]=NB[i]=i;

	int ok=0,count=0;

	do{
		do{
			int win=0;
			rep(i,N){
				if(A[NA[i]]>B[NB[i]]) win++;
				else win--;
			}
			if(win>0) ok++;
			count++;
		}while(next_permutation(all(NA)));
	}while(next_permutation(all(NB)));

	cout<<setprecision(10)<<(double)ok/count<<endl;
}