#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
#define pb push_back
#define rep(i, n) for (int i = 0; i < (n); i++)
#define reps(i, n) for (int i = 1; i <= (n); i++)
#define for_(i, a, b) for (int i = (a); i < (b); i++)
#define all(v) v.begin(), v.end()
#define Yes(b) ((b) ? "Yes" : "No")
#define YES(b) ((b) ? "YES" : "NO")
template <typename T>
inline bool chmin(T &a, const T &b)
{
  bool compare = a > b;
  if (a > b)
    a = b;
  return compare;
}
template <typename T>
inline bool chmax(T &a, const T &b)
{
  bool compare = a < b;
  if (a < b)
    a = b;
  return compare;
}
template <typename T>
T gcd(T a, T b)
{
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}
template <typename T>
inline T lcm(T a, T b) { return (a * b) / gcd(a, b); }
template <typename T>
inline T ceil(T a, T b) { return (a + (b - 1)) / b; }
template <typename T>
inline T floor(T a, T b) { return a / b; }

int main()
{
  int N;
  cin >> N;
  vector<int> A(N);
  rep(i, N)
  {
    cin >> A[i];
  }
  vector<int> B(N);
  rep(i, N)
  {
    cin >> B[i];
  }
  sort(all(A));
  sort(all(B));
  ll ans = 0;
  ll sum = 0;
  do
  {
    vector<int> B_copy = B;
    do
    {
      int cnt = 0;
      rep(i, N)
      {
        if (A[i] > B[i])
          cnt++;
      }
      if (cnt > N / 2)
      {
        ans++;
      }
      sum++;
    } while (next_permutation(all(B_copy)));

  } while (next_permutation(all(A)));

  cout << (double)ans / (double)sum << endl;
  return 0;
}