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

int main()
{
	int p[] = {0,1,2,3};
	int N , A[4], B[4];
	cin >> N;
	for(int i=0; i<N; i++){
		cin >> A[i];
	}
	for(int i=0; i<N; i++){
		cin >> B[i];
	}

	int total = 0;
	int tawin = 0;
	do{
		total++;
		int awin=0, bwin=0;
		for(int i=0; i<N; i++){
			if(A[i] > B[p[i]]){
				awin++;
			} else {
				bwin++;
			}
		}
		if(awin > bwin){
			tawin ++;
		}
	}while(next_permutation(p, p+N));

	cout << (double)tawin / (double)total << endl;

	return 0;
}