#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
using ll = long long;
int ctoi(char c){return c-'0';}
ll ctoll(char c){return c-'0';}

int main(){
    int n;
    cin >> n;
    vector<int>a(n);
    vector<int>b(n);
    rep(i,n)cin >> a[i];
    rep(i,n)cin >> b[i];

    sort(a.begin(),a.end());
    sort(b.begin(),b.end());

    double sum = 0;
    double kati = 0;

    do{
        
        do{
            int tmp = 0;
            rep(i,n){
                if(a[i] > b[i])tmp++;
            }
            if(tmp > n/2)kati++;
            sum++;
        }while(next_permutation(b.begin(),b.end()));

    }while(next_permutation(a.begin(),a.end()));

    //cout << sum << " " << kati << endl;
    printf("%.5f\n",kati/sum);
}