#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
//using mint = static_modint<998244353>;
//using mint = modint;
using mint = static_modint<1000000007>;
using vm = vector<mint>;
using vvm = vector<vm>;
ostream &operator<<(ostream &o,const mint &m){cout<<m.val();return o;}
using ll = long long;
using vl = vector<ll>;
using vvl = vector<vl>;
using pl = pair<ll,ll>;
using vp = vector<pl>;
#define rep(i,n) for(ll i=0;i<(ll)(n);++i)
#define reps(i,s,n) for(ll i=(s);i<(ll)(n);++i)
#define rep1(i,n) for(ll i=1;i<=(ll)(n);++i)
#define chmin(x,y) x=min(x,y)
#define chmax(x,y) x=max(x,y)
#define fi first
#define se second
#define pb push_back
#define eb emplace_back
const long long INF = 1e18;

#ifdef DEBUG
#include <debug.hpp>
#endif

int main(){
#ifdef DEBUG
	cout << "--- Input ---" << endl;
#endif
	ll N;cin>>N;
	vl A(N),B(N);
	rep(i,N)cin>>A.at(i);
	rep(i,N)cin>>B.at(i);
	sort(A.begin(),A.end());
	sort(B.begin(),B.end());
#ifdef DEBUG
	cout << "--- Logic ---" << endl;
#endif
	ll a=0,n=0;
	do{
		do{
			ll p=0;
			rep(i,N){
				if(A.at(i)>B.at(i))++p;
			}
			if(p>N/2)++a;
			++n;
		}while(next_permutation(B.begin(),B.end()));
	}while(next_permutation(A.begin(),A.end()));
#ifdef DEBUG
	cout<<"a="<<a<<" n="<<n<<endl;
	cout << "--- Answer ---" << endl;
#endif
	cout << fixed << setprecision(9);
	cout<<(double)a/(double)n<<endl;
	return 0;
}
//cout << fixed << setprecision(9);