#include<iostream>
#include<vector>
#include<algorithm>
#include<cstdio>
#include<string>
using namespace std;

int main(){
	int n;
	cin>>n;
	vector<int>a(n),b(n),c(n);
	for(int i=0;i<n;i++){
		cin>>a[i];
		c[i]=i;
	}
	for(int i=0;i<n;i++){
		cin>>b[i];
	}
	int num=0,win=0,all=0;
	do{
		num=0;
		for(int i=0;i<n;i++){
			if(a[c[i]]>b[i])num++;
			else if(a[c[i]]<b[i])num--;
		}
		if(num>0)win++;
		all++;
	}while(next_permutation(c.begin(),c.end()));
	printf("%lf",(double(win)/all));
	return 0;
}