#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define all(a) a.begin(),a.end()
#define reps(i, a, n) for (int i = (a); i < (int)(n); i++)
#define rep(i, n) reps(i, 0, n)
#define rreps(i, a, n) for (int i = (a); i > (int)(n); i--)
const long long mod = 1000000007;
const long long INF = 1e18;

int main() {
  int n;
  cin >> n;
  vector<int> a (n);
  vector<int> b (n);
  rep(i,n) {
    cin >> a[i];
  }
  rep(i,n) {
    cin >> b[i];
  }
  sort(all(a));
  sort(all(b));
  int aw = 0;
  int bw = 0;
  int ac,bc;
  do {
    do {
      ac = 0;
      bc = 0;
      rep(i,n) {
        if (a[i] > b[i]) {
          ac++;
        }
        else {
          bc++;
        }
      }
      if (ac > bc) {
        aw++;
      }
      else {
        bw++;
      }
    } while (next_permutation(all(a)));
  } while (next_permutation(all(b)));
  cout << fixed << setprecision(8);
  cout << aw / (double)(aw+bw) << endl;
  return 0;
}