#include <bits/stdc++.h>
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.at(i);
  for (int i=0; i<N; i++) cin >> B.at(i);
  
  double num = 1.0;
  for (int i=1; i<=N; i++) num *= i; 
  double res = 0;
  int n = N/2;
  sort(B.begin(), B.end());
  do {
    int c = 0;
    for(int i=0; i<N; i++){
      if(A.at(i) > B.at(i)) c++;
    }
    if(c > n) res++;
  } while (next_permutation(B.begin(), B.end()));

  cout << res / num << endl;
  
  return 0;
}