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

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