#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main(){
    int n;
    cin >> n;
    vector<int> a(n), b(n);
    for(auto&& i : a){
        cin >> i;
    }
    for(auto&& i : b){
        cin >> i;
    }
    sort(begin(a), end(a));
    sort(begin(b), end(b));
    int cnt = 0;
    double ans = 0;
    do{
        do{
            cnt++;
            int win = 0;
            for(int i = 0; i < n; i++){
                win += b[i] < a[i];
            }
            ans += n < win * 2;
        }while(next_permutation(begin(b), end(b)));
    }while(next_permutation(begin(a), end(a)));
    ans /= cnt;
    cout << fixed << ans << "\n";
}