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

int main()
{
int N;scanf("%d",&N);
vector<int> order(N);
for(int i=0;i<N;i++)order[i]=i;
vector<int> A(N),B(N);
for(int i=0;i<N;i++)scanf("%d ",&A[i]);
for(int i=0;i<N;i++)scanf("%d ",&B[i]);
sort(A.begin(),A.end());sort(B.begin(),B.end());
int totalwin=0,total=0;
do{
    do{
        int win=0;
        total++;
        for(int i=0;i<N;i++){if(A[i]>B[i])win++;}
        if(win>N/2)totalwin++;
    }while(next_permutation(B.begin(),B.end()));
}while(next_permutation(A.begin(),A.end()));
printf("%lf",(double)totalwin/total);    
}