#include<iostream>
#include<vector>
#include<algorithm>
#include<cctype>
#include<utility>
#include<string>
#include<cstring>
#include<cmath>
#include<numeric>
#include<queue>
#include<climits>
#include<cstdio>


#define REP(i, n) for(int i = 0;i < n;i++)
#define REPR(i, n) for(int i = n;i >= 0;i--)
#define FOR(i, m, n) for(int i = m;i < n;i++)
#define FORR(i, m, n) for(int i = m;i >= n;i--)
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define llong long long
#define pb(a) push_back(a)
//#define INF ((LLONG_MAX) / (2))
using namespace std;
typedef pair<int, int> P;
typedef pair<llong, llong> LP;
typedef pair<int, P> PP;
typedef pair<llong, LP> LPP;
typedef long long int ll;
typedef pair<ll,int> LL_IP;
typedef pair<ll,ll> LL_LLP;
#define INF 1e9+7
#define ARRAY_MAX 100005

int main(){

    int n;
    cin >> n;
    int total = 0;
    vector<int> a(n),b(n);
    REP(i,n){
        cin >> a[i];
    }
    REP(i,n){
        cin >> b[i];
    }
    VSORT(a);
    VSORT(b);

    int times = 0;
    int p = 0;
    do{
      
        do{
            total++;
            int a_win = 0;
            int b_win = 0;
            REP(i,n){
                if(a[i] > b[i]){
                    a_win++;
                }else{
                    b_win++;
                }
            }
            if(a_win > b_win){
                times++;
            }
        }while(next_permutation(b.begin(),b.end()));

    }while(next_permutation(a.begin(),a.end()));
    double ans = times/(double)total;
    printf("%.5f\n",ans);

    return 0;
}