#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n;
	cin >> n;
	vector<int>A(n);
	vector<int>B(n);
	vector<int>indexs(n);
	vector<vector<int>>permulation_memo;
	for (int i = 0; i < n; i++)
	{
		cin >> A.at(i);
		indexs.at(i) = i;
	}
	for (int i = 0; i < n; i++)
		cin >> B.at(i);
	int A_win_total = 0;
	int total = 0;
	do
	{
		permulation_memo.push_back(indexs);
	} while (next_permutation(indexs.begin(), indexs.end()));
	for (vector<int>indexsA : permulation_memo)
	{
		
		for (vector<int>indexsB : permulation_memo)
		{
			total++;
			int A_win = 0;
			int B_win = 0;
			for (int i = 0; i < n; i++)
			{
				if (A.at(indexsA.at(i)) < B.at(indexsB.at(i)))
					B_win++;
				else
					A_win++;
			}
			if (A_win > B_win)
				A_win_total++;
		}
	}
	cout << (double)A_win_total / (double)total << endl;
}