#include <bits/stdc++.h>
#define debug(x) cerr << #x << ": " << x << '\n';
using namespace std;
using ll = long long;
using P = pair<int, int>;
const int INF = (int)1e9;

int main(void){
	int N; cin >> N;
	int a[4], b[4];
	for(int i = 0; i < N; i++) cin >> a[i];
	for(int i = 0; i < N; i++) cin >> b[i];

	sort(a, a+N); sort(b, b+N);

 	int win = 0, game = 0;
	do{
		game++;
		int w = 0, l = 0;
		for(int i = 0; i < N; i++){
			if(a[i] > b[i]) w++;
			else if(a[i] < b[i]) l++;
		}
		if(w > l) win++;
	}while(next_permutation(a, a+N));

	printf("%lf\n", (double)win/game);

	return 0;
}