#include<fstream.h>
#include<math.h>
#include<algorithm>
#include<iomanip.h>
using namespace std;
 
struct punct{
    double x,y,d;
};
 
punct p[120000],p0,s[120000];
 
 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;
    }
 
 int compara (const void * a, const void * b)
{
  //return ( *(int*)a - *(int*)b );
 
 
 
 punct A,B;
 
    A=*(punct*)a;
    B=*(punct*)b;
    double pr=prod(p[1],B,A);
    if(pr<0)return -1;
    if(pr==0&&A.d>B.d)return -1;
    if(A.x==B.x&&A.y==B.y)return 0;
    return 1;
    }
             
 
 
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=1;
    for (i=2;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[1],p[im]);
}
 
 
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 main()
{long i,m;
    ifstream f("infasuratoare.in");
    ofstream g("infasuratoare.out");
    f>>n;
    for (i=1;i<=n;++i) f>>p[i].x>>p[i].y;
    cauta_primul();
    p0=p[1];
    for (i=2;i<=n;i++) p[i].d=dist(p0,p[i]);
                         
    qsort(p+2,n-1,sizeof(punct),compara);
     
    i=1;
    s[1]=p[1];
    s[2]=p[2];
    m=2;
    for (j=3;j<=n;++j)
        if (prod(p0,p[j-1],p[j])>0){++m;s[m]=p[j];}
     
     
    for (j=1;j<=m;++j) p[j]=s[j];
    n=m;
    ps=3;
    for (i=4;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<<"\n";
    for (i=1;i<=ps;++i)
        {g<<fixed<<s[i].x<<' '<<s[i].y<<"\n";
             
        }
    f.close();
    g.close();
    return 0;
}