#include<iostream>
using namespace std;
int n;
int a[4],b[4];
bool A[4],B[4];
double f(int i,int as,int bs)
{
	if(n==i)
	{
		return as>bs;
	}
	else
	{
		double ans=0,cnt=0;
		for(int j=0;j<n;j++)
		{
			for(int k=0;k<n;k++)
			{
				if(A[j]||B[k])continue;
				A[j]=B[k]=1;
				ans+=f(i+1,as+(a[j]>b[k]),bs+(a[j]<b[k]));
				cnt+=1;
				A[j]=B[k]=0;
			}
		}
		return ans/cnt;
	}
}
main()
{
	cin>>n;
	for(int i=0;i<n;i++)
	{
		cin>>a[i];
	}
	for(int i=0;i<n;i++)cin>>b[i];
	cout<<f(0,0,0)<<endl;
}