/**
 * yukicoder No.133
 */
#include <iostream>
#include <vector>
#include <algorithm>

typedef std::vector<int> VI;

int main()
{
  int N, num_win, num_game, each_win;
  std::cin >> N;
  VI A(N), B(N);
  for (int i = 0; i < N; i++) std::cin >> A.at(i);
  for (int i = 0; i < N; i++) std::cin >> B.at(i);

  std::sort(A.begin(), A.end());
  std::sort(B.begin(), B.end());
  num_win = 0, num_game = 0;
  do {
    do {
      each_win = 0;
      for (int i = 0; i < N; i++)
      {
        if (A.at(i) > B.at(i))
          each_win++;
        else if (A.at(i) < B.at(i))
          each_win--;
      }
      if (each_win > 0)
        num_win++;
      num_game++;
    } while(std::next_permutation(B.begin(),B.end()));
  } while(std::next_permutation(A.begin(), A.end()));
  std::cout << (double)num_win/(double)num_game << "\n";
}