#include <iostream>
#include <algorithm>
#include <vector>
#include <numeric>

using namespace std;

int main(int argc, char const* argv[])
{
	int n;
	cin >> n;
	int *a = new int[n];
	int *b = new int[n];
	for(int i = 0; i < n; i++){
			cin >> a[i];
	}
	for(int i = 0; i < n; i++){
			cin >> b[i];
	}
	vector<int> vec(n);
	iota(vec.begin(), vec.end(), 1);
	int all = 0;
	int win = 0;
	do{
			int count = 0;
			for(int i = 0; i < n; i++){
					if(a[i] > b[vec[i] - 1])count++;
			}
			if(count > n - count)win++;
			all++;
	}while(next_permutation(vec.begin(), vec.end()));
	cout << (double)win / (double)all << endl;
	return 0;
}