#include<bits/stdc++.h>
using namespace std;
using uint = unsigned int;
using ll = long long;
using ull = unsigned long long;
template<class T> using V = vector<T>;
template<class T> using VV = V<V<T>>;
template<class T> using VVV = V<VV<T>>;
template<class T> using VVVV = VV<VV<T>>;
#define rep(i,n) for(ll i=0ll;i<n;i++)
#define REP(i,a,n) for(ll i=a;i<n;i++)
const long long INF = (1LL << 60);
const long long mod99 = 998244353;
const long long mod107 = 1000000007;
const long long mod = mod99;
#define eb emplace_back
#define pb eb
#define be(v) (v).begin(),(v).end()
#define all(i,v) for(auto& i : v)
#define all2(i,j,v) for(auto& [i,j] : v)
template<class T, class U> void chmin(T& t, const U& u) { if (t > u) t = u; }
template<class T, class U> void chmax(T& t, const U& u) { if (t < u) t = u; }

// cin.tie(nullptr);
// ios::sync_with_stdio(false);
// cout << fixed << setprecision(20);

void solve(){
  ll n;
  cin >> n;
  V<ll> a(n), b(n);
  rep(i,n) cin >> a[i];
  rep(i,n) cin >> b[i];
  sort(be(a));
  sort(be(b));
  ll ans = 0;
  ll cnt = 0;
  do{
  	cnt ++;
  	ll cc = 0;
  	rep(i, n){
  		if(a[i] < b[i]) cc--;
  		if(a[i] > b[i]) cc++;
  	}
  	if(cc>0) ans++;
  }while(next_permutation(be(a)));
  cout << fixed << setprecision(20);
  cout << 1.0*ans/cnt << endl;
  
}





int main(){
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  int t=1;
  // cin >> t;
  rep(i,t) solve();
}