#include <bits/stdc++.h>
using namespace std;

int n;
int a[5], b[5];
int p, q;
double ans;

int main(){
//	cin.tie(0);
//	ios::sync_with_stdio(false);
	cin >> n;
	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);
	do{
		do{
			++q;
			int tmp[3] = {};
			for(int i=0; i<n; ++i){
				if(a[i] > b[i]) ++tmp[0];
				else if(a[i] < b[i]) ++tmp[2];
				else ++tmp[1];
			}
			if(tmp[0] > tmp[2]) ++p;
		}while(next_permutation(b, b+n));
	}while(next_permutation(a, a+n));
	ans = (double)p / q;
	printf("%.5lf\n", ans);
}