#include <iostream>
#include <algorithm>
using namespace std;

int main(){
	int all = 0,win = 0,n;
	cin >> n;
	int a[n],b[n],numa[n];
	for(int i = 0;i < n;i++){
		cin >> a[i];
		numa[i] = i;
	}
	for(int i = 0;i < n;i++) cin >> b[i];
	do{
		int count = 0;
		for(int i = 0;i < n;i++) count += (a[numa[i]] > b[i] ? 1 : -1);
		if(count > 0) win++;
		all++;
	}while(next_permutation(numa,numa + n));
	cout << double(win) / all << endl;
}