#include<bits/stdc++.h>
using namespace std;

#define int long long

typedef pair<int,int>pint;
typedef vector<int>vint;
typedef vector<pint>vpint;
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)
#define each(it,v) for(__typeof((v).begin()) it=(v).begin();it!=(v).end();it++)
template<class T,class U>void chmin(T &t,U f){if(t>f)t=f;}
template<class T,class U>void chmax(T &t,U f){if(t<f)t=f;}


int N;
int A[10],B[10];

signed main(){
    cin>>N;
    rep(i,N)cin>>A[i];
    rep(i,N)cin>>B[i];

    sort(A,A+N);sort(B,B+N);
    int tmp=0,hoge=0;
    do{
        do{
            int cnt=0;
            rep(i,N)if(A[i]>B[i])cnt++;
            if(cnt>N/2)hoge++;
            tmp++;
        }while(next_permutation(B,B+N));
    }while(next_permutation(A,A+N));

    printf("%.20lf\n",1.0*hoge/tmp);
    return 0;
}