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

int main(){
  int N; cin >> N;
  vector<int> a(N);
  vector<int> b(N);

  for(int i = 0;i < N;i++)cin >> a[i];
  for(int i = 0;i < N;i++)cin >> b[i];

  sort(a.begin(),a.end());
  sort(b.begin(),b.end());

  vector<vector<int>> a_perm;
  vector<vector<int>> b_perm;

  do{
    a_perm.push_back(a);
  }while(next_permutation(a.begin(),a.end()));


  do{
    b_perm.push_back(b);
  }while(next_permutation(b.begin(),b.end()));

  int perm_num = a_perm.size();

  double ans = 0;

  for(int i = 0;i < perm_num;i++){
    for(int j = 0;j < perm_num;j++){
      int a_wins = 0;
      for(int k = 0;k < N;k++){
        if(a_perm[i][k] > b_perm[j][k])a_wins++;
      }

      if(a_wins > N/2)ans++;
    }
  }

  ans = ans/(perm_num*perm_num);

  printf("%.10lf\n",ans);




}