#include <bits/stdc++.h>
#define int long long
using namespace std;
int inf=1e18;
signed main(){
    int n;cin>>n;
    double ans=0;
    vector<int>a(n),b(n);
    for(int i=0;i<n;i++)cin>>a[i];
    for(int i=0;i<n;i++)cin>>b[i];
    vector<int>p(n);
    for(int i=0;i<n;i++)p[i]=i;
    double down=1;
    for(int i=0;i<n;i++)down*=i+1;
    for(int i=0;i<n;i++)down*=i+1;
    // cout<<fixed<<setprecision(18)<<down<<endl;
    // return 0;
    do{
        vector<int>p2(n);
        for(int i=0;i<n;i++)p2[i]=i;
        do{
            double cnt=0;
            for(int i=0;i<n;i++)if(a[p[i]]>b[p2[i]])cnt++;
            if(cnt>=(n+1)/2){
                ans+=(double)1/down;
            }
        }while(next_permutation(p2.begin(),p2.end()));
    }while(next_permutation(p.begin(),p.end()));
    cout<<fixed<<setprecision(18)<<ans<<endl;
}