/**
 * yukicoder 133
 * カードゲーム
 *
 * next_permutation
 */
#include <iostream>
#include <algorithm>
#include <cassert>
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() {
  // 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));

  return won;
}

int C[MAX_N];
bool used[MAX_N];
int dfs(int pos, int *target) {
  if (pos == N) {
    int win{};
    for (int i{}; i < N; ++i) {
      if (A[i] > C[i]) ++win;
    }
    return win > N / 2 ? 1 : 0;
  }
  int result{};
  for (int i{}; i < N; ++i) {
    if (!used[i]) {
      C[pos] = target[i];
      used[i] = true;
      result += dfs(pos + 1, target);
      used[i] = false;
    }
  }

  return result;
}

int main() {
  scanf("%d", &N);
  for (int i{}; i < N; ++i) scanf("%d", &A[i]);
  for (int i{}; i < N; ++i) scanf("%d", &B[i]);
  int won1 = next_permutation_solve();
  int won2 = dfs(0, B);
  assert(won1 == won2);
  printf("%f\n", static_cast<double>(won1) / factorial(N));
  return 0;
}