#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
#include <cstring>
#include <deque>
#include <iomanip>
#include <limits>
#include <fstream>
using namespace std;
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)
#define CLR(mat) memset(mat, 0, sizeof(mat))
typedef long long ll;
int main()
{
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;cin>>n;
  vector<int> v1(n),v2(n);
  FOR(i,0,n)cin>>v1[i];
  FOR(i,0,n)cin>>v2[i];
  sort(v1.begin(),v1.end());
  sort(v2.begin(),v2.end());
  double ans=0.0;
  int step=0;
  do{
    do{
      step++;
      int cnt=0;
      FOR(i,0,n){
        if(v1[i]>v2[i])cnt++;
      }
      if(cnt>n/2)ans+=1.0;
    }while(next_permutation(v2.begin(),v2.end()));
  }while(next_permutation(v1.begin(),v1.end()));
  cout<<ans/step<<endl;
}