#include <bits/stdc++.h>

//const static double	de_PI	= 3.14159265358979323846;
//const static int	de_MOD	= 1000000007;
//const static int	de_MAX	= 999999999;
//const static int	de_MIN = -999999999;

inline int Factorial(const int n) {
	int ans = 1;
	for (int i = 1; i <= n; i++) { ans *= i; }
	return(ans);
}

int main(void) {

	//std::ifstream in("123.txt");	std::cin.rdbuf(in.rdbuf());

	int N = 0;
	std::cin >> N;
	int facN = Factorial(N);

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

	std::sort(A.begin(), A.end());
	std::sort(B.begin(), B.end());

	double ans = 0;
	for (int i = 0; i < facN; i++) {
		for (int j = 0; j < facN; j++) {
			int a = 0, b = 0;
			for (int k = 0; k < N; k++) {
				if (A[k] > B[k]) { a++; }
				else { b++; }
			}
			if (a > b) { ans++; }
			std::next_permutation(B.begin(), B.end());
		}
		std::next_permutation(A.begin(), A.end());
	}

	std::cout << ans / (facN * facN) << std::endl;
}