#include <bits/stdc++.h>
using namespace std;
using ll = long long;

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 child, mother;
  child = mother = 0;
  do {
    do {
      int cnt = 0;
      for (int i = 0; i < N; i++) {
        if (A[i] > B[i]) cnt++;
      }
      if (cnt > N-cnt) child++;
      mother++;
    } while (next_permutation(A.begin(), A.end()));
  } while (next_permutation(B.begin(), B.end()));
  cout << fixed << setprecision(10) << 1.0*child/mother << endl;
  return 0;
}