#include <bits/stdc++.h>

using namespace std;
#define ll long long
#define REP(i,x) for(int i=0;i<(int)(x);i++)
#define REPS(i,x) for(int i=1;i<=(int)(x);i++)
#define RREP(i,x) for(int i=((int)(x)-1);i>=0;i--)
#define RREPS(i,x) for(int i=((int)(x));i>0;i--)
const ll mod = 1e9 + 7;
typedef pair<int,int>           PI;
typedef pair<ll,ll>             PL;
typedef vector<PI>               vip; 
typedef vector<int>             vi;
typedef vector<vi>              vvi;
typedef vector<ll>              vl;
typedef vector<vl>              vvl;

int fact(int k){
    return k==0 ? 1 : k * fact(k-1);
}






int main (){
    cin.tie(0);
    ios::sync_with_stdio(false);
    
    int n;
    cin >> n;
    vi a(n);
    vi b(n);
    REP(i,n) {
        cin >> a[i];
    }
    REP(i,n) {
        cin >> b[i];
    }
    int perm = fact(n);

    float won = 0;
    for(int i = 0; i < perm; i++){//かつ回数数える


        REP(j,perm){
            int count = 0;
            int cont = 0;
            REP(d,n){
                if(a[d] - b[d] > 0){
                    count++;
                }
                if(a[d] - b[d] < 0){
                    cont++;
                }
            }
            if(count > cont) won++;




            next_permutation(b.begin(), b.end());
        }





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

    perm *= perm;
    float ans = won / perm;

    cout << ans << endl;




    return 0;
}