#include <iostream>
#include <fstream>
#include <algorithm>
#include <vector>
#define NMAX 120005
#define x first
#define y second
using namespace std;

const double EPS = 1e-12;
pair<double,double> v[NMAX];
vector <pair<double,double>> sol;
int n;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
double det(pair<double,double>a,pair<double,double>b,pair<double,double>c)
{
    return (a.x-c.x)*(b.y-c.y)-(b.x-c.x)*(a.y-c.y);
}
/*void solve_1()
{
    sol.push_back({v[n-2].x,v[n-2].y});
    sol.push_back({v[n-3].x,v[n-3].y});
    for(int i=n-4;i>=0;i--)
    {
        int m=sol.size();
        double rez=det(sol[m-2],sol[m-1],v[i]);
        while(rez<EPS)
        {
            m--;
            sol.pop_back();
            rez=det(sol[m-2],sol[m-1],v[i]);
        }
        sol.push_back({v[i].x,v[i].y});
    }
}*/
void solve_2()
{
    sol.push_back({v[0].x,v[0].y});
    sol.push_back({v[1].x,v[1].y});
    int p=1,k=1;
    for(int i=2;i>=0;i+=(p=(i==n-1)?-p:p))
    {
        int m=sol.size();
        double rez=det(sol[m-2],sol[m-1],v[i]);
        while(rez<=EPS&&m>k)
        {
            m--;
            sol.pop_back();
            rez=det(sol[m-2],sol[m-1],v[i]);
        }
        sol.push_back({v[i].x,v[i].y});
        if(i==n-1)k=sol.size();
    }
}
int main()
{
    f>>n;
    for(int i=0;i<n;i++)
    {
        double a,b;
        f>>a>>b;
        v[i]={a,b};
    }
    sort(v,v+n);
    for(int i=0;i<n;i++)
         cout<<v[i].x<<" "<<v[i].y<<"\n";
    solve_2();
    //solve_1();
    g<<sol.size()-1<<"\n";
    for(int i=0;i<=sol.size()-2;i++)
        g<<fixed<<sol[i].x<<" "<<sol[i].y<<"\n";
    return 0;
}