#include <bits/stdc++.h>

using namespace std;

ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");

struct point{
	double x, y;
}v[120100], st[120100];

int n, vf;

double det(point A, point B, point C)
{
  return A.x*B.y + C.x*A.y + B.x*C.y - C.x*B.y - A.x*C.y - B.x*A.y;
// sau return (A.x - B.x) * (A.y - C.y) - (A.y - B.y) * (A.x - C.x);
}



int comp1(point A, point B)
{
  if(A.x==B.x) return (A.y<B.y);
  else return (A.x<B.x);
}

int comp2(point B, point C)
{
  return (det(v[1],B,C) < 0);
}

int main()
{ int i;
  f>>n;
  for(i=1;i<=n;i++)
    f>>v[i].x>>v[i].y;

  sort(v+1,v+n+1,comp1);
	st[1]=v[1];

  sort(v+2,v+n+1,comp2);
  st[2]=v[2];

  vf = 2;

  for(i=3;i<=n;i++)
    {
      while(vf>2 && det(st[vf-1],st[vf],v[i])>0) vf--;
      st[++vf]=v[i];
    }

  g<<vf<<'\n';
  for(i=vf;i>=1;i--)
    g<<fixed<<setprecision(6)<<st[i].x<<" "<<st[i].y<<" "<<'\n';

  return 0;
}