#include<stdio.h>
#include<stdlib.h>
#define EPS 1e-12
#define Nmax 120002
struct Punct
 {
  double x,y;
 };
Punct c[Nmax], a[Nmax];
int st[Nmax];
int H,n;
Punct sol[Nmax];
void read()
 {
  int i;
  scanf("%d",&n);
  for(i=1;i<=n;++i)
   scanf("%lf%lf",&c[i].x,&c[i].y);
 }
inline int comp(double a, double b)
 {
  if(a+EPS < b) return -1;//a<b
  if(b+EPS < a) return 1;  //a>b
  return 0; // a==b
 }
int cmp(const void*a, const void*b)
 {
  int x=*(int*)a, y=*(int*)b;
  int r=comp(c[x].x, c[y].x);
  if(!r)
   {
    int k=comp(c[x].y, c[y].y);
    return k;
   }
  return r;
 }
void sortare()
 {
  int i,h[Nmax];
  for(i=0;i<=n;++i) h[i]=i;
  c[0].x=c[0].y=-1000000003;
  qsort(h,n+1,sizeof(int),cmp);
  for(i=1;i<=n;++i) a[i]=c[h[i]];
 }
int viz[Nmax];
inline int tre_scos(Punct A, Punct B, Punct C)
 {
  double det = A.x*B.y + B.x*C.y + A.y*C.x;
  det -= ( B.y*C.x + A.y*B.x + C.y*A.x );
  if(det<0) return -1;
  if(det==0) return 0;
  return 1;
 }
void convex()
 {
  int pas=1,i,k=0;
  viz[2]=1; st[1] = 1; st[2] = 2; k=2; i=3;
  while(!viz[1])
   {
    while(viz[i])
     {
      if(i==n) pas=-1;
      i+=pas;
     }
    while(k>=2 && tre_scos(a[st[k-1]], a[st[k]], a[i]) == -1) viz[st[k--]] = 0;
    st[++k] = i; viz[i] = 1;
   }
  H = k-1;
  printf("%d\n",H);
  for(i=1;i<=H;++i)  printf("%.6lf %.6lf\n",a[st[i]].x, a[st[i]].y);
 }
int main()
 {
  freopen("infasuratoare.in","r",stdin);
  freopen("infasuratoare.out","w",stdout);
  read();
  sortare();
  convex();
  return 0;
  }