#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using pii = pair<int, int>;

int main() {
  cin.tie(0);
  ios_base::sync_with_stdio(false);
  cout << fixed << setprecision(10);
  
  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());

  int all = 0, win = 0;
  do {
    vector<int> c = b;
    do {
      int num = 0;
      for (int i = 0; i < N; i++) {
        num += a[i] > c[i];
      }
      win += num * 2 > N;
      all++;
    } while (next_permutation(c.begin(), c.end()));
  } while (next_permutation(a.begin(), a.end()));
  cout << 1. * win / all << endl;

  return 0;
}