#include <bits/stdc++.h>
using namespace std;
// # define all(v) v.begin(),v.end()

int main(){
    int N; cin >> N;
    int a[N]; for(int i=0; i<N; i++) cin >> a[i];
    int b[N]; for(int i=0; i<N; i++) cin >> b[i];
    sort(a,a+N);
    sort(b,b+N);
    int Wa = 0;
    do{
        do{
            int wa = 0, wb = 0;
            for(int i=0; i<N; i++){
                wa += (a[i]>b[i]);
                wb += (a[i]<b[i]);
            }
            Wa += (wa>wb);
        }while(next_permutation(b,b+N));
    }while(next_permutation(a,a+N));
    function<int(int)> nPn = [&](int n){
        if(n==1) return 1;
        return n * nPn(n-1); 
    };
    int sum = nPn(N); sum *= sum;
    double r = (1.0*Wa) / (1.0*sum);
    cout << r << endl;
    return 0;
}