#include<stdio.h>
#define nx 120005
#define inf 1000000001
struct asd
 {
  double x,y;
 };
asd a[nx];
int v[nx];
int n,p;

int cmp (int x,int y,int z)
 {
  double s=(a[x].x-a[z].x)*(a[y].y-a[z].y)-(a[x].y-a[z].y)*(a[y].x-a[z].x);
  if (s>0) return 1;
  if (s<0) return -1;
  return 0;
 }

void sort (int st,int dr)
 {
  int i=st,j=dr,r=(st+dr)/2;
  asd s;
  do {
   while (cmp(1,i,r)==1) ++i;
   while (cmp(1,r,j)==1) --j;
   if (i<=j) {
     s=a[i];
     a[i]=a[j];
     a[j]=s;
     i++,--j;
   }
  } while (i<=j);
  if (st<j) sort(st,j);
  if (i<dr) sort(i,dr);
 }

int main()
 {
  freopen ("infasuratoare.in","r",stdin);
  freopen ("infasuratoare.out","w",stdout);
  int n,i;
  a[0].x=inf;
  a[0].y=inf;
  scanf("%d",&n);
  for (i=1;i<=n;++i) {
    scanf("%lf%lf",&a[i].x,&a[i].y);
    if (a[i].y<a[p].y || (a[i].y==a[p].y && a[i].x<a[p].x))
      p=i;
   }
  a[0]=a[p],a[p]=a[1],a[1]=a[0];
  sort(2,n);
  v[++v[0]]=1;
  for (i=2;i<=n;++i)
   {
    while (v[0]>1 && cmp(v[v[0]-1],v[v[0]],i)==-1) --v[0];
    v[++v[0]]=i;
   }
  printf("%d\n",v[0]);
  for (i=1;i<=v[0];++i)
   printf ("%.6f %.6f\n",a[v[i]].x,a[v[i]].y);
  return 0;
 }