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

//typedef
typedef unsigned int UINT;
typedef unsigned long long ULL;
typedef long long LL;
typedef pair<long long, long long> PLL;
typedef tuple<long long, long long, long long> TLL3;
typedef tuple<long long, long long, long long, long long> TLL4;
typedef set<LL, greater<LL> > setdownLL;
#define PQ priority_queue
typedef PQ<LL, vector<LL>, greater<LL> > pqupLL;
//container utill
#define ALL(v) (v).begin(),(v).end()
#define CR [](auto element1, auto element2){return element1>element2;}
#define LB lower_bound
#define UP upper_bound
#define PB push_back
#define MP make_pair
#define MT make_tuple
//constant
#define PI 3.141592653589793

int main(){
    //input
    int N;
    cin >> N;
    int A[N], B[N];
    int i;
    for(i=0; i<N; i++){
        cin >> A[i];
    }
    for(i=0; i<N; i++){
        cin >> B[i];
    }

    //calc
    sort(A,A+N);
    sort(B,B+N);
    int Awon=0, shobusu=0;
    int Awonsho, Bwonsho;
    do{
        do{
            Awonsho=0, Bwonsho=0;
            for(i=0; i<N; i++){
                if(A[i]>B[i]) Awonsho++;
                else if(A[i]<B[i]) Bwonsho++;
            }
            if(Awonsho>Bwonsho) Awon++;
            shobusu++;
        }while(next_permutation(B,B+N));
    }while(next_permutation(A,A+N));
    long double  Awonlb=Awon, shobusulb=shobusu;

    //output
    cout << fixed << setprecision(5) << Awonlb/shobusulb << endl;
    return 0;
}