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

int f(int n){
    if(n == 1) return 1;
    else return n * f(n - 1);
}

int main(){
    int n;
    cin >> n;
    vector<int> a(n), b(n);
    for(int i = 0; i < n; i++) cin >> a[i];
    for(int i = 0; i < n; i++) cin >> b[i];
    sort(a.begin(), a.end());
    sort(b.begin(), b.end());
    int k = n / 2 + 1;
    int cnt = 0;
    int all = f(n) * f(n);
    do{
        do{
            int aw = 0;
            for(int i = 0; i < n; i++){
                if(a[i] > b[i]) aw++;
            }
            if(aw >= k) cnt++;

        }while(next_permutation(a.begin(), a.end()));
    }while(next_permutation(b.begin(), b.end()));

    long double ans = (long double)cnt / all;
    cout << ans << endl;
    return 0; 
}