#include <iostream>
#include <set>
#include <vector>
#include <sstream>
using namespace std;

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

bool selected_A[MAX_N]{};
bool selected_B[MAX_N]{};
set<pair<int, int>> combi;
set<set<pair<int, int>>> collection;

void dfs(int num) {
  if (num == N) {
    collection.insert(combi);
    return;
  }

  ++num;
  for (int i{}; i < N; ++i) {
    if (selected_A[i]) continue;
    selected_A[i] = true;
    for (int j{}; j < N; ++j) {
      if (selected_B[j]) continue;
      selected_B[j] = true;
      auto p = make_pair(A[i], B[j]);
      combi.insert(p);
      dfs(num);
      combi.erase(p);
      selected_B[j] = false;
    }
    selected_A[i] = false;
  }
}

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]);

  dfs(0);
  int won{};
  for (auto& c : collection) {
    int win{};
    for (auto& p : c) {
      if (p.first > p.second) ++win;
    }
    if (win > N - win) ++won;
  }

  printf("%f\n", won / static_cast<double>(collection.size()));
  return 0;
}