#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
using namespace std;
int main(){
	cout << fixed << setprecision(5);
	int N;
	cin >> N;
	vector<int> A(N);
	for (int i = 0; i < N; i++){
		cin >> A[i];
	}
	vector<int> B(N);
	for (int i = 0; i < N; i++){
		cin >> B[i];
	}
	vector<int> p(N);
	for (int i = 0; i < N; i++){
		p[i] = i;
	}
	int cnt1 = 0;
	int cnt2 = 0;
	while (1){
		int a = 0;
		int b = 0;
		for (int i = 0; i < N; i++){
			if (A[i] > B[p[i]]){
				a++;
			}
			if (A[i] < B[p[i]]){
				b++;
			}
		}
		if (a > b){
			cnt1++;
		}
		cnt2++;
		if (!next_permutation(p.begin(), p.end())){
			break;
		}
	}
	cout << (double) cnt1 / cnt2 << endl;
}