#include<iostream>
#include<vector>
#include<algorithm>
#include<map>
#include<set>
#include<cmath>
#include<queue>
#include<stack>
#include<string>

#define rep(i,n) for(int i=0;i<(n);i++)

using ll = long long;
using namespace std;

int main() {
	int n;
	cin >> n;
	vector<int> a(n), b(n);
	rep(i, n) cin >> a[i];
	rep(i, n) cin >> b[i];

	vector<int> da(n), db(n);
	rep(i, n) da[i] = i;

	int num = 0, win = 0;
	do {
		rep(i, n) db[i] = i;
		do {
			num++;
			int wina = 0, winb = 0;
			rep(i, n) {
				if (a[da[i]] > b[db[i]]) wina++;
				else winb++;
			}
			if (wina > winb) win++;
		} while (next_permutation(db.begin(), db.end()));
	} while (next_permutation(da.begin(), da.end()));

	double ans = (double)win / (double)num;
	printf("%.4f", ans);

	return 0;
}