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

int main() {
  int n;
  cin >> n;
  vector<int> a(n), 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 cnt=0;
  double total=0;
  sort(a.begin(), a.end());
  do {
    sort(b.begin(), b.end());
    do {
      int win_a=0, win_b=0;
      for (int i=0; i<n; i++) {
        if (a.at(i) > b.at(i)) win_a++;
        if (b.at(i) > a.at(i)) win_b++;
      }
      if (win_a > win_b) cnt++;
      total++;
    } while (next_permutation(b.begin(), b.end()));
  } while (next_permutation(a.begin(), a.end()));
  
  double prob = cnt / total;
  cout << prob << endl;
}