#include <algorithm>
#include <iostream>
#include <vector>

using namespace std;

int main() {
  int n;
  cin >> n;

  vector<int> a(n), 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());

  double ans = 0;

  int c = 0;
  do {
    do {
      c++;
      int cnt1 = 0, cnt2 = 0;
      for (int i = 0; i < n; i++) {
        cnt1 += (a[i] > b[i]);
        cnt2 += (a[i] < b[i]);
      }
      ans += (cnt1 > cnt2);
    } while (next_permutation(b.begin(), b.end()));
  } while (next_permutation(a.begin(), a.end()));

  ans /= c;

  cout << ans << "\n";

  return 0;
}