#include<fstream>
#include<math.h>
#include<algorithm>
#include<iomanip.h>
using namespace std;
struct punct{double x,y,d;
            }p[120000],p0,s[120000];
long i,n,k,j,ps;
double pr;
 
inline void sch(punct &q,punct &w)
{
    punct aux;
    aux=q;q=w;w=aux;
}
 
void cauta_primul()
{
    long i,im;
    im=0;
    for (i=1;i<n;i++)
        if (p[i].y<p[im].y) im=i;
            else if (p[i].y==p[im].y && p[i].x<p[im].x) im=i;
             
    sch(p[0],p[im]);
}
 
inline double prod(punct A,punct B,punct C)
{
    return A.x*B.y+B.x*C.y+C.x*A.y-B.y*C.x-C.y*A.x-A.y*B.x;
}
 
double dist(punct A, punct B)
{
    double u,v;
    u=A.x-B.x;
    v=A.y-B.y;
    return sqrt(u*u+v*v);
}
 
int compara (punct u, punct  v)
{
    
    double pr;
    pr=prod(p0,v,u);
    if(u.x==v.x &&u.y==v.y)return 0;
    if (pr<0||pr==0&&u.d>v.d) return -1;
    return 1;
}

         
int main()
{long i;
    ifstream f("infasuratoare.in");
    ofstream g("infasuratoare.out");
    f>>n;
    for (i=0;i<n;++i) f>>p[i].x>>p[i].y;
    cauta_primul();
    p0=p[0];
    for (i=1;i<n;i++) p[i].d=dist(p0,p[i]);
                         
    i=n-1;
    punct *t;
    t=p+1; 
    sort(p+1,p+n+1,compara);
    i=1;
    s[0]=p[0];
    s[1]=p[1];
     
    for (j=2;j<n;++j)
        if (prod(p0,p[j-1],p[j])>0){++i;s[i]=p[j];}
     
     
    for (j=0;j<=i;++j) p[j]=s[j];
    n=i+1;
    ps=2;
    for (i=3;i<n;++i)
    {
        do
        {
            pr=prod(s[ps-1],s[ps],p[i]);
            if (pr<0) --ps;
        }while(pr<0);
        s[++ps]=p[i];
    }
    g<<ps+1<<"\n";
    for (i=0;i<=ps;++i)
        {g<<fixed<<s[i].x<<' '<<s[i].y<<"\n";
             
        }
    f.close();
    g.close();
    return 0;
}