#include <bits/stdc++.h>

using namespace std;

typedef pair<int,int> P;
typedef pair<int,pair<int,int>> PP;
typedef long long ll;

const double EPS = 1e-8;
const int INF = 1e9;
const int MOD = 1e9+7;

int dy[] = {0,1,0,-1};
int dx[] = {1,0,-1,0};

int main(void) {
	int n;
	cin >> n;
	vector<int> a(n),b(n);
	for(int i=0;i<n;i++){
		cin >> a[i];
	}
	for(int i=0;i<n;i++){
		cin >> b[i];
	}
	sort(a.begin(),a.end());
	sort(b.begin(),b.end());
	int win,cnt;
	win = cnt = 0;
	do{
		do{
			int w=0,l=0;
			for(int i=0;i<n;i++){
				if(a[i] > b[i])w++;
				else if(b[i] > a[i])l++;
			}
			if(w > l)win++;
			cnt++;
		}while(next_permutation(b.begin(),b.end()));
	}while(next_permutation(a.begin(),a.end()));

	//cout << win << " " << cnt << endl;
	cout << fixed << setprecision(10) << (double)win/cnt << endl;
	return 0;
}