#include <fstream>
#include <algorithm>
#include <cmath>
#include <iomanip>
using namespace std;
struct vct
{
    double x,y;
}v[120000];
struct stiva
{
    double x,y,z;
}t1[80000],t2[80000];
bool cmp (vct A ,vct B)
{
    if(A.y==B.y)
        return A.x>B.x;
    else
    return A.y<B.y;
}
double tg(double b , double a)
{
    a=a-v[1].y;
    b=abs(b-v[1].x);
    if(a==0)
    return 1000;
    else
    return b/a;
}
double c;
int i,n,k=1,p=1;
int main()
{
    ifstream f("infasuratoare.in");
    ofstream g("infasuratoare.out");

    f>>n;
    for(i=1;i<=n;i=i+1)
    {
        f>>v[i].x;
        f>>v[i].y;
    }
    sort(v+1,v+1+n,cmp);

    t1[1].x=v[1].x ; t1[1].y=v[1].y ;
    t2[1].x=v[1].x ; t2[1].y=v[1].y ;

    for(i=2;i<=n;i=i+1)
    {
        if(v[i].x>=v[1].x)
        {
            if(v[i].x<t1[k].x)
            {
                t1[++k].x=v[i].x;
                t1[k].y=v[i].y;
                t1[k].z=tg(v[i].x,v[i].y);
            }
            else
            {
                c=tg(v[i].x,v[i].y);
                while(c>t1[k].z && k>1)
                    k--;
                t1[++k].x=v[i].x;
                t1[k].y=v[i].y;
                t1[k].z=c;
            }
        }
        else
        {
            if(v[i].x>t2[p].x)
            {
                t2[++p].x=v[i].x;
                t2[p].y=v[i].y;
                t2[p].z=tg(v[i].x,v[i].y);
            }
            else
            {
                c=tg(v[i].x,v[i].y);
                while(c>t2[p].z && p>1)
                    p--;
                t2[++p].x=v[i].x;
                t2[p].y=v[i].y;
                t2[p].z=c;
            }
        }
    }

g<<k+p-1<<'\n';
    for(i=1;i<=k;i=i+1)
    g<<fixed<<setprecision(6)<<t1[i].x<<' '<<fixed<<setprecision(6)<<t1[i].y<<'\n';
    for(i=p;i>=2;i--)
    g<<fixed<<setprecision(6)<<t2[i].x<<' '<<fixed<<setprecision(6)<<t2[i].y<<'\n';




    return 0;
}