#include <iostream>
#include <algorithm>
using namespace std;

/**
 * @brief nの階乗（組み合わせ数）<br>
 * intで出力できるのは13まで<br>
 * longで出力できるのは???まで
 */
template <typename T>
T factorial(T n) {
  for (T i = n - 1; i > 1; --i)
    n *= i;
  return n;
}

static const int MAX_N = 4;

int main() {
  int N;
  int A[MAX_N];
  int B[MAX_N];
  cin >> N;
  for (int i = 0; i < N; ++i) {
    cin >> A[i];
  }
  for (int i = 0; i < N; ++i) {
    cin >> B[i];
  }

  int all_num = factorial(N);

  sort(A, A + N); // 昇順にソートしておく必要あり
  int won = 0;
  do {
    int win = 0;
    for (int i = 0; i < N; ++i) {
      if (A[i] > B[i])
        ++win;
    }
    if (win > N / 2)
      ++won;
  } while (next_permutation(A, A + N));

  cout << static_cast<double>(won) / all_num  << endl;
}