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

#define int long long
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define repi(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define all(x) (x).begin(),(x).end()
#define pb push_back
#define mp make_pair
#define mt make_tuple

typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;

const int inf = 1LL<<60;
const int mod = 1e9 + 7;
const double eps = 1e-9;

/*{
}*/

signed main()
{
  int n;
  cin >> n;

  vi a(n), b(n);
  rep(i, n) cin >> a[i];
  rep(i, n) cin >> b[i];

  sort(all(a));
  sort(all(b));

  int ans = 0, cnt = 0;
  do{
    do{
      cnt++;

      int win = 0;
      rep(i, n){
        if(a[i] > b[i]) win++;
        else win--;
      }

      if(win > 0) ans++;
      
    }while(next_permutation(all(b)));
  }while(next_permutation(all(a)));

  printf("%.9f\n", (double)ans/cnt);

  return 0;
}