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

using namespace std;
typedef long long ll;
#define rep(i, s, e) for (int(i) = (s); (i) <= (e); ++(i))
#define all(x) x.begin(),x.end()


int main()
{
	int n; cin >> n;
	vector<int> a(n), b(n), perm(n);
	rep(i, 0, n - 1)
	{
		cin >> a[i];
		perm[i] = i;
	}
	rep(i, 0, n - 1)cin >> b[i];

	double cntN = 0;
	double allN = 0;
	do
	{
		int tempA = 0;
		int tempB = 0;
		rep(i, 0, n - 1)
		{
			if (a[i] > b[perm[i]])++tempA;
			if (a[i] < b[perm[i]])++tempB;
		}
		if (tempA > tempB)++cntN;
		++allN;
	} while (next_permutation(all(perm)));

	cout << cntN / allN << endl;
}