#include<algorithm>
#include<iostream>
#include<string>
#include<math.h>
#include<iomanip>
#include<queue>
#include<set>

#define ull unsigned long long
#define ll long long
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
 
using namespace std;


int main()
{
    int N, win=0;
    vector<int> A;
    vector<int> B;

    cin >> N;

    A.resize(N);
    B.resize(N);


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

    sort(A.begin(), A.end());
    sort(B.begin(), B.end());

    int cnt,round=0;
    do{
        do{
            cnt = 0;
            round++;
            rep(i,N)
                if(A[i]>B[i])
                    cnt++;
            if(N/2<cnt)
                win++;
        }while(next_permutation(B.begin(), B.end()));
    }while(next_permutation(A.begin(), A.end()));

    cout << (float)win/(float)round << endl;
    return 0;
}