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

int main() {
	int N;
	int A[4],B[4];
	cin >> N;
	for (int i = 0; i < N; i++) cin >> A[i];
	for (int i = 0; i < N; i++) cin >> B[i];
	sort(A, A + N);
	sort(B, B + N);

	int p = 0;
	int n = 0;
	do {
		do {
			p++;
			int m = 0;
			for (int i = 0; i < N; i++) {
				if (A[i] > B[i]) m++;
			}
			if (m > N - m) n++;
		} while (next_permutation(B, B + N));
	} while (next_permutation(A, A + N));

	cout << (double) n / p << endl;
}