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

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());
  int victory = 0;
  int cnt = 0;
  
  do{
    do{
    cnt++;
      int a = 0;
    for(int i = 0; i < N; i++){
      if( A[i] > B[i]){ a++;}}
      
      if( N%2){
        if( a >= (N+1)/2){ victory++;}}
      else{
        if( a > N/2){ victory++;}}
      
    }while(next_permutation(B.begin(),B.end()));
  }while(next_permutation(A.begin(),A.end()));
  
  
  cout << fixed << setprecision(10) << (double) victory/cnt << endl; return 0;}