#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define INF 1LL<<60
int main(){
    
    ll n,a=0,b=0;cin>>n;
    vector<ll> f(n),g(n);
    for(auto& i:f)cin>>i;
    for(auto& i:g)cin>>i;
    sort(f.begin(),f.end());
    sort(g.begin(),g.end());
    do{
        do{
            ll sub=0,ass=0;
            for(ll i=0;i<n;i++){
                if(f[i]>g[i])sub++;
                else ass++;
            }
            if(sub>ass)a++;
            else if(sub<ass)b++;
        }while(next_permutation(g.begin(),g.end()));
    }while(next_permutation(f.begin(),f.end()));
    cout<<fixed<<setprecision(10)<<(ld)a/(ld)(a+b)<<endl;
}