#include<bits/stdc++.h>
using namespace std;
using ll = long long;
const int INF = 1<<30 ;
const ll INFLL = 1LL<<60;
const int MOD = 998244353;
#define rep(i,l,n) for(int i=l;i<n;i++)
#define per(i,l,r) for(int i=r;i>=l;i--)
#define test ifs("1test_inputs.txt")//ifstream test;
//=====================================================================================================================================================================
int main(){
  int N; cin >> N;
  vector<int> a(N), b(N);
  rep(i,0,N) cin >> a[i];
  rep(i,0,N) cin >> b[i];
  sort(a.begin(), a.end());
  sort(b.begin(), b.end());

  int cnt_win = 0;
  int cnt_all = 0;
  do {
    do {
      int cnt = 0;
      rep(i,0,N){
        if(a[i] > b[i]) cnt++;
      }
      if(cnt > N/2) cnt_win++;
      cnt_all++;

    } while (next_permutation(b.begin(), b.end()));
  } while (next_permutation(a.begin(), a.end()));

  cout << cnt_win/(double)cnt_all << endl;
  return 0;
  }