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

int main() {
  int n;
  std::cin >> n;
  
  std::vector<int> indices1(n);
  std::vector<int> indices2(n);
  std::iota(indices1.begin(), indices1.end(), 0);

  std::vector<int> cardsA(n);
  std::vector<int> cardsB(n);
  for (auto& e : cardsA) {
    std::cin >> e;
  }
  for (auto& e : cardsB) {
    std::cin >> e;
  }
  
  int fact = 1;
  for (int i = 1; i <= n; i++) {
    fact *= i;
  }

  int total = fact * fact;
  int win = 0;
  do {
    std::iota(indices2.begin(), indices2.end(), 0);
    do {
      int a = 0;
      int b = 0;
      for (int i = 0; i < n; i++) {
	if (cardsA[indices1[i]] > cardsB[indices2[i]]) {
	  a++;
	} else if (cardsA[indices1[i]] < cardsB[indices2[i]]) {
	  b++;
	}
      }
      if (a > b) {
	win++;
      }
    } while (std::next_permutation(indices2.begin(), indices2.end()));
  } while (std::next_permutation(indices1.begin(), indices1.end()));

  float ans = (float) win / total;
  
  std::cout << ans << std::endl;

  return 0;
}