#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, n) for (int i = a; i < n; i++)
using ll = long long;
using ld = long double;
using pl = pair<ll, ll>;
using vl = vector<ll>;
using vvl = vector<vl>;
using vb = vector<bool>;
using vvb = vector<vb>;
using vc = vector<char>;
using vvc = vector<vc>;
const int mod = 998244353;
const ll hashh = 2147483647;

int main(){
    ll n,point = 0;
    ld pt = 0,yes = 0;
    cin >> n;
    vl a(n),b(n);
    rep(i,0,n) cin >> a[i];
    rep(i,0,n) cin >> b[i];
    sort(a.begin(),a.end());
    sort(b.begin(),b.end());
    do{
        do{
            point = 0;
            rep(i,0,n){
                if(a[i] > b[i]){
                    point++;
                }
            }
            pt++;
            if(point > n/2){
                yes++;
            }
        }while(next_permutation(a.begin(),a.end()));
    }while(next_permutation(b.begin(),b.end()));
    printf("%.10Lf\n",yes/pt);
    return 0;
}