#include <stdio.h>
#include <math.h>
#include <cmath>
using namespace std;
#define dim 120005
#define lm 0.000000000001
FILE *f=fopen("infasuratoare.in","r");
FILE *g=fopen("infasuratoare.out","w");
typedef struct
 {
 double x,y,u1,u2;       
 } Punct;
long n,k;
Punct p[dim],s[dim];
void swap(Punct &p1,Punct &p2)
 {
 Punct px=p1;
 p1=p2;
 p2=px;
 }
void read()
 {
 long i,j=1;
 Punct pv;
 fscanf(f,"%ld",&n);
 for(i=1;i<=n;i++)
  {
  fscanf(f,"%lf %lf",&p[i].x,&p[i].y);
  if(i==1||(p[i].y-pv.y<0)||(abs(p[i].y-pv.y)<=lm&&p[i].x-pv.x<0))
   {
   pv=p[i];
   j=i;
   }
  }
 swap(p[1],p[j]);
 }
void assign()
 {
 long i;
 for(i=2;i<=n;i++)
  {
  p[i].u1=p[i].x-p[1].x;
  p[i].u2=p[i].y-p[1].y;
  }
 }
void qsort(long l,long r)
 {
 long i,j;
 j=l-1;
 for(i=l;i<=r;i++)
  {
  if(p[i].u2*p[r].u1<=p[r].u2*p[i].u1)
   swap(p[i],p[++j]);
  }
 if(l<j-1)
  qsort(l,j-1);
 if(r>j+1)
  qsort(j+1,r);
 }
double clock(Punct p1,Punct p2,Punct p3)
 {
 return ((p3.x-p1.x)*(p2.y-p1.y)-(p3.y-p1.y)*(p2.x-p1.x));
 }
void graham()
 {
 assign();
 qsort(2,n);
 s[++k]=p[n+1]=p[1];
 long i;
 for(i=2;i<=n;i++)
  {
  if(clock(s[k],p[i],p[i+1])<0)
   s[++k]=p[i];
 // else
  // k--;
  }
 }
void show()
 {
 fprintf(g,"%ld\n",k);
 long i;
 for(i=1;i<=k;i++)
  fprintf(g,"%.6lf %.6lf\n",s[i].x,s[i].y);
 }
int main()
 {
 long i;
 read();
 graham();
 show();
 return 0;
 }