/*
    Author:zeke
    
    pass System Test!
    GET AC!!
*/
#include <iostream>
#include <queue>
#include <vector>
#include <iostream>
#include <vector>
#include <string>
#include <cassert>
#include <algorithm>
#include <functional>
#include <cmath>
#include <queue>
#include <set>
#include <stack>
#include <deque>
#include <map>
#include <iomanip>
#include <utility>
#include <stack>
using ll = long long;
using ld = long double;
using namespace std;
#define rep(i, n) for(int i = 0; i < (int)(n); i++)
#define all(x) (x).begin(),(x).end()
#define rep3(var, min, max) for (ll (var) = (min); (var) < (max); ++(var))
#define repi3(var, min, max) for (ll (var) = (max) - 1; (var) + 1 > (min); --(var))
#define Mp(a,b) make_pair((a),(b))
#define F first
#define S second
#define Icin(s) ll (s);cin>>(s);
#define Scin(s) ll (s);cin>>(s);
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
typedef pair<ll, ll> P;
typedef vector<ll> V;
typedef vector<V> VV;
typedef vector<P> VP;
//ここから
struct BipartiteMatching {
  vector< vector< int > > graph;
  vector< int > match, alive, used;
  int timestamp;

  BipartiteMatching(int n) : graph(n), alive(n, 1), used(n, 0), match(n, -1), timestamp(0) {}

  void add_edge(int u, int v) {
    graph[u].push_back(v);
    graph[v].push_back(u);
  }

  bool dfs(int idx) {
    used[idx] = timestamp;
    for(auto &to : graph[idx]) {
      int to_match = match[to];
      if(alive[to] == 0) continue;
      if(to_match == -1 || (used[to_match] != timestamp && dfs(to_match))) {
        match[idx] = to;
        match[to] = idx;
        return true;
      }
    }
    return false;
  }

  int bipartite_matching() {
    int ret = 0;
    for(int i = 0; i < graph.size(); i++) {
      if(alive[i] == 0) continue;
      if(match[i] == -1) {
        ++timestamp;
        ret += dfs(i);
      }
    }
    return ret;
  }

  void output() {
    for(int i = 0; i < graph.size(); i++) {
      if(i < match[i]) {
        cout << i << "-" << match[i] << endl;
      }
    }
  }
};
//BipartiteMatching(n)　頂点n個
//add_edge(s,t)
//bipartite_matching()最大マッチング数
int main() {
    int n;cin>>n;
    V vec1(n);
    rep(i,n)cin>>vec1[i];
    V vec2(n);
    rep(i,n)cin>>vec2[i];
    sort(all(vec1));
    sort(all(vec2));
    ld c=0;
    int k=0;
    do{
        sort(all(vec1));
        do{
            k++;
            int s=0;
            int e=0;
            rep(i,n){
                if(vec1[i]>vec2[i])s++;
                else e++;
            }
            if(s>e)c++;
        }while(next_permutation(all(vec1)));
    }while(next_permutation(all(vec2)));
    cout<<setprecision(20)<<(ld)c/k<<endl;
}