#include <bits/stdc++.h>


using namespace std;
typedef long long ll;

#define REP(i,n) for(ll i=0; i<ll(n); i++)
#define FOR(i,m,n) for(ll i=ll(m); i<ll(n); i++)
#define ALL(obj) (obj).begin(),(obj).end()
#define VI vector<int>
#define VP vector<pair<int,int>>
#define VPP vector<pair<int,pair<int,int>>>
#define VLL vector<long long>
#define VVI vector<vector<int>>
#define VVLL vector<vector<long long>>
#define VC vector<char>
#define VS vector<string>
#define VVC vector<vector<char>>
#define VB vector<bool>
#define VVB vector<vector<bool>>
#define fore(i,a) for(auto &i:a)
typedef pair <int, int> P;
template<typename T> using min_priority_queue = priority_queue<T, vector<T>, greater<T>>;

const int  INF = 1 << 29;
const ll INFL = 1LL << 60;
const ll mod = 1000000007;



int main() {
	

	int n;
	cin >> n;
	VI a(n), b(n);
	REP(i, n)cin >> a[i];
	REP(i, n)cin >> b[i];
	sort(ALL(a));
	sort(ALL(b));

	double win = 0;
	double lose = 0;

	do {
		do {
			int c = 0;
			int d = 0;
			REP(i, n) {
				if (a[i] > b[i])c++;
				else d++;
			}
			if (c > d)win++;
			lose++;
		} while (next_permutation(ALL(b)));
	} while (next_permutation(ALL(a)));

	
	cout << fixed << setprecision(15) << win / lose << endl;


}