/**
 * yukicoder 133
 * カードゲーム
 *
 * next_permutation
 */
#include <iostream>
#include <algorithm>
using namespace std;

inline int factorial(int n) {
  int f{1};
  for (int i{2}; i <= n; ++i) f *= i;
  return f;
}

constexpr int MAX_N = 4;
int N;
int A[MAX_N];
int B[MAX_N];

int next_permutation_solve() {
  scanf("%d", &N);
  for (int i{}; i < N; ++i) scanf("%d", &A[i]);
  for (int i{}; i < N; ++i) scanf("%d", &B[i]);

  // next_permutationを正常に動作させるためには
  // あらかじめ昇順にソートしておく必要あり
  sort(B, B+N);
  int won{};
  do {
    int win{};
    for (int i{}; i < N; ++i) {
      if (A[i] > B[i]) ++win;
    }
    if (win > N / 2) ++won;
  } while (next_permutation(B, B+N));

  printf("%f\n", static_cast<double>(won) / factorial(N));
  return 0;
}

int main() {
  return next_permutation_solve();
}