#include <bits/stdc++.h>

using namespace std;

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());
    double max = 0;
    double vic = 0;
    do
    {
        do
        {
            max++;
            int judge = 0;
            for(int i = 0; i < N; i++)
            {
                if(A[i] > B[i]) judge++;
                if(A[i] < B[i]) judge--;
            }
            if(judge > 0) vic++;
        }while(next_permutation(B.begin(),B.end()));
        sort(B.begin(),B.end());
    }while(next_permutation(A.begin(),A.end()));
    double p = vic / max;
    cout << fixed << setprecision(5) << p << endl;
}