#include<bits/stdc++.h>
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
typedef long long ll;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);   

    int n;
    cin >> n;

    int a[n],b[n];
    rep(i,n) cin >> a[i];
    rep(i,n) cin >> b[i];

    sort( a, a + n);
    sort( b, b + n);

    int all = 0, awin = 0;

    do{
        sort( a, a + n);
        do{
            all++;
            int temp = 0;
            rep(i,n) if(a[i] > b[i]) temp++;
            if(temp > n/2) awin++;
        }while(next_permutation(a, a + n));
    }while(next_permutation(b, b + n));

    //cout << "awin:" << awin << endl;
    //cout << "all:" << all << endl;

    double ans = (double)awin/(double)all;

    printf("%.10lf\n",ans);

    return 0;
}