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

using namespace std;

int main(){
    int N;
    cin >> N;
    vector<int> A(N);
    vector<int> B(N);
    vector<int> C(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());
    C=B;
    double total=0;
    double per=0;
    do{
        do{
            int win=0;
            int t=0;
            for(int i=0;i<N;i++){
                if(A[i]>B[i]){
                    win++;
                }
                t++;
            }
            if(win*2>t){
                per++;
            }
            total++;
        }while(next_permutation(B.begin(),B.end()));
        B=C;
    }while(next_permutation(A.begin(),A.end()));
    double ans=per/total;
    cout << fixed << setprecision(10);
    cout << ans << endl;
}