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

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

  sort(A.begin(), A.end());
  sort(B.begin(), B.end());

  int a = 0;
  do {
    do {
      int aa = 0, bb = 0;
      for (int i = 0; i < N; ++i) {
        if (A[i] > B[i])
          ++aa;
        if (A[i] < B[i])
          ++bb;
      }

      if (aa > bb)
        ++a;
    } while (next_permutation(B.begin(), B.end()));

    sort(B.begin(), B.end());
  } while (next_permutation(A.begin(), A.end()));

  int u = 1;
  for (int i = 1; i <= N; ++i)
    u *= i;
  u *= u;

  cout << a * 1.0 / u << endl;
}