#include <bits/stdc++.h>
#include <atcoder/all>
#include <unordered_set>
#include <functional>
using namespace std;
using namespace atcoder;
using ll = long long;
using P = pair<int, int>;
#define rep(i, n) for (int i = 0; i < (n); i++)
//void chmin(ll & a, ll b) { a = min(a, b); }
using mint = modint998244353;

bool num[100000000];

int main() {
	int n;
	cin >> n;
	vector<int> a(n), b(n);
	rep(i, n) cin >> a[i];
	rep(i, n) cin >> b[i];
	sort(a.begin(), a.end());
	sort(b.begin(), b.end());
	int al = 0;
	int win = 0;
	do {
		do {
			int cnta = 0;
			int cntb = 0;
			rep(i, n) {
				if (a[i] > b[i]) {
					cnta++;
				}
				else if (a[i] == b[i]) {

				}
				else {
					cntb++;
				}
			}
			if (cnta > cntb) {
				win++;
			}
			al++;
		} while (next_permutation(b.begin(), b.end()));
	} while (next_permutation(a.begin(), a.end()));

	double ans = double(win)/al;
	cout << ans << endl;
}