#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define all(v) v.begin(), v.end()
typedef pair<int, int> P;

const int INF = 1001001001;
const vector<int> di = {-1, 0, 1, 0};
const vector<int> dj = {0, -1, 0, 1};

int n;
vector<int> card_a;
vector<int> card_b;

int main() {
  cin >> n;
  card_a.resize(n);
  card_b.resize(n);

  rep(i, n) { cin >> card_a[i]; }
  rep(i, n) { cin >> card_b[i]; }

  sort(all(card_a));
  sort(all(card_b));

  double cnt = 0;
  double total = 0;

  do {
    do {
      total++;
      int vic_a = 0;
      int vic_b = 0;

      rep(i, n) {
        if (card_a[i] > card_b[i]) {
          vic_a++;
        } else if (card_a[i] < card_b[i]) {
          vic_b++;
        }
      }

      if (vic_a > vic_b) {
        cnt++;
      }
    } while (next_permutation(all(card_b)));
  } while (next_permutation(all(card_a)));

  printf("%f\n", cnt / total);
}