#include <iostream>
#include <algorithm>

using namespace std;

int a[5], b[5];

int main(){
	cout.setf(ios::fixed);
	cout.precision(100);


	int n;
	cin >> n;
	for (int i = 0; i < n; ++i) cin >> a[i];
	for (int i = 0; i < n; ++i) cin >> b[i];
	sort(b, b + n);

	int w = 0, total = 0;
	do{
		sort(a, a + n);
		do{
			int cnt = 0;
			for (int i = 0; i < n; ++i){
				if (a[i] > b[i]) ++cnt;
				else --cnt;
			}
			if (cnt > 0)++w;
			++total;
		} while (next_permutation(a, a + n));
	} while (next_permutation(b, b + n));

	cout << 1.*w / total << endl;

}