#include "bits/stdc++.h"
using namespace std;


int main() {
	int N;
	cin >> N;
	vector<int> A(N);
	vector<int> B(N);
	for (int i = 0; i < N; i++)
	{
		cin >> A[i];
	}
	for (int i = 0; i < N; i++)
	{
		cin >> B[i];
	}

	vector<int> NA(N);
	for (int i = 0; i < N; i++)
	{
		NA[i] = i;
	}
	int ok = 0;
	int count = 0;
	do{
		int win = 0;
		for (int i = 0; i < N; i++)
		{
			if (A[NA[i]] > B[i]) win++;
			else win--;
		}
		if (win > 0) ok++;
		count++;
	} while (next_permutation(NA.begin(), NA.end()));

	printf("%.14f\n", (double)ok / count);
}