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

int main() {
  int N; cin >> N;
  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];
  int winA = 0, game = 0;
  int perm[N];
  for (int i = 0; i < N; i++) perm[i] = i;
  do {
    int a = 0, b = 0;
    for (int i = 0; i < N; i++) {
      if (A[i] > B[perm[i]]) a++;
      else b++;
    }
    if (a > b) winA++;
    game++;
  } while (next_permutation(perm, perm + N));
  double ans = 1.0 * winA / game;
  cout << ans << endl;
  return 0;
}