#include <iostream>
#include <vector>
#include <algorithm>
#include <iomanip>
using namespace std;

int main(){
    int n;
    cin >> n;
    vector<int> a(n), b(n);
    for(auto &p: a) cin >> p;
    for(auto &p: b) cin >> p;

    int total = 0;
    int win = 0;
    sort(a.begin(), a.end());
    sort(b.begin(), b.end());
    do{
        //vector<int> b(n);
        //for(int i = 0; i < n; i++) b[i] = b0[i];
        do{
            int awin = 0;
            for(int i = 0; i < n; i++){
                if(a[i] > b[i]) awin++;
            }
            if(awin > n/2) win++;
            total++;
        }while(next_permutation(b.begin(), b.end()));
    }while(next_permutation(a.begin(), a.end()));

    cout << fixed << setprecision(10) << (long double)win/total << endl;
    return 0;
}