#include<iostream>
#include<vector>
#include<algorithm>
#define REP(i,n) for(int i=0;i<n;i++)
#define ALL(s) s.begin(),s.end()
using namespace std;
int main(void){
	int n; cin >> n;
	vector<int> a(n), b(n);
	REP(i, n){ cin >> a[i]; }
	REP(i, n){ cin >> b[i]; }
	sort(ALL(a));
	int win = 0, total = 0;
	do{
		sort(ALL(b));
		do{
			int cnt = 0;
			REP(i, n){ (a[i] > b[i]) ? cnt++ : cnt--; }
			if (cnt > 0) win++;
			total++;
		} while (next_permutation(ALL(b)));
	} while (next_permutation(ALL(a)));
	cout << (double)win / total << endl;
	return 0;
}