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

int main() {
  int N;
  std::cin >> N;
  std::vector<int> A(N), B(N);
  for (int i=0; i<N; i++) std::cin >> A[i];
  for (int i=0; i<N; i++) std::cin >> B[i];
  std::sort(std::begin(A), std::end(A));
  std::sort(std::begin(B), std::end(B));
  int total = 0;
  int n_win = 0;
  do {
    do {
      int score = 0;
      for (int i=0; i<N; i++) {
        if (A[i] > B[i]) {
          score++;
        } else if (A[i] < B[i]) {
          score--;
        }
      }
      if (score > 0) n_win++;
      total++;
    } while( std::next_permutation(std::begin(B), std::end(B)) );
  } while( std::next_permutation(std::begin(A), std::end(A)) );
  std::cout << static_cast<double>(n_win) / total << std::endl;
  
}