#include<bits/stdc++.h>
#define f first
#define s second
#define mp make_pair
#define inf 100000000
#define eps (1e-11)
#define equals(a,b) (fabs((a)-(b))<eps)
using namespace std;

class Point{
public:
  double x,y;
  Point(double x=0,double y=0):x(x),y(y){}

  Point operator+(Point p){ return Point(x+p.x,y+p.y);}
  Point operator-(Point p){ return Point(x-p.x,y-p.y);}
  Point operator*(double k){ return Point(x*k,y*k);}
  Point operator/(double k){ return Point(x/k,y/k);}
  bool operator<(Point p)const{ return (x!=p.x ? x<p.x : y<p.y);}
  bool operator==(Point p)const{ return fabs(x-p.x)<eps && fabs(y-p.y)<eps;}

  double abs(){ return sqrt(norm());}
  double norm(){ return (x*x+y*y);}
};
typedef Point Vector;
typedef vector<Point> Polygon;

class Segment{
public:
  Point p1,p2;
  Segment(Point p1,Point p2):p1(p1),p2(p2){}
};
typedef Segment Line;

class Circle{
public:
  Point c;
  double r;
  Circle(Point c=Point(),double r=0.0):c(c),r(r){}
};

double norm(Vector a){ return (a.x*a.x+a.y*a.y);}
double abs(Vector a){ return sqrt(norm(a));}
double dot(Vector a,Vector b){ return (a.x*b.x+a.y*b.y);}
double cross(Vector a,Vector b){ return (a.x*b.y-a.y*b.x);}

Point project(Segment s,Point p){
  Vector base=(s.p2-s.p1);
  double r=(dot(p-s.p1,base)/base.norm());
  return (s.p1+base*r);
}

Point reflect(Segment s,Point p){
  return p+(project(s,p)-p)*2;
}

bool isOrthogonal(Vector a,Vector b){
  return equals(dot(a,b),0.0);
}

bool isParallel(Vector a,Vector b){
  return equals(cross(a,b),0.0);
}

static const int COUNTER_CLOCKWISE=1;
static const int CLOCKWISE=-1;
static const int ONLINE_BACK=2;
static const int ONLINE_FRONT=-2;
static const int ON_SEGMENT=0;

int ccw(Point p0,Point p1,Point p2){
  Vector a=p1-p0;
  Vector b=p2-p0;
  if(cross(a,b)>eps)return COUNTER_CLOCKWISE;
  if(cross(a,b)<-eps)return CLOCKWISE;
  if(dot(a,b)<-eps)return ONLINE_BACK;
  if(a.norm()<b.norm())return ONLINE_FRONT;
  return ON_SEGMENT;
}

bool intersect(Point p1,Point p2,Point p3,Point p4){
  return (ccw(p1,p2,p3)*ccw(p1,p2,p4)<=0 &&
          ccw(p3,p4,p1)*ccw(p3,p4,p2)<=0);
}

bool intersect(Segment s1,Segment s2){
  return intersect(s1.p1,s1.p2,s2.p1,s2.p2);
}

Point getCrossPoint(Segment s1,Segment s2){
  Vector base=s2.p2-s2.p1;
  double d1=abs(cross(base,s1.p1-s2.p1));
  double d2=abs(cross(base,s1.p2-s2.p1));
  double t=d1/(d1+d2);
  return (s1.p1+(s1.p2-s1.p1)*t);
}

double getDistanceLP(Line l,Point p){
  return abs(cross(l.p2-l.p1,p-l.p1)/abs(l.p2-l.p1));
}

double getDistanceSP(Segment s,Point p){
  if(dot(s.p2-s.p1,p-s.p1)<0.0)return abs(p-s.p1);
  if(dot(s.p1-s.p2,p-s.p2)<0.0)return abs(p-s.p2);
  return getDistanceLP(s,p);
}

double getDistance(Segment s1,Segment s2){
  if(intersect(s1,s2))return 0.0;
  return min(min(getDistanceSP(s1,s2.p1),getDistanceSP(s1,s2.p2)),
             min(getDistanceSP(s2,s1.p1),getDistanceSP(s2,s1.p2)));
}

pair<Point,Point> getCrossPoints(Circle c,Line l){
  Vector pr=project(l,c.c);
  Vector e=(l.p2-l.p1)/abs(l.p2-l.p1);
  double base=sqrt(c.r*c.r-norm(pr-c.c));
  return mp(pr+e*base,pr-e*base);
}

double arg(Vector p){ return atan2(p.y,p.x);}
Vector polar(double a,double r){ return Point(cos(r)*a,sin(r)*a);}

pair<Point,Point> getCrossPoints(Circle c1,Circle c2){
  double d=abs(c1.c-c2.c);
  double a=acos((c1.r*c1.r+d*d-c2.r*c2.r)/(2*c1.r*d));
  double t=arg(c2.c-c1.c);
  return mp(c1.c+polar(c1.r,t+a),c1.c+polar(c1.r,t-a));
}

double getPolygonArea(Polygon p){
  double area=0.0;
  int n=p.size();
  for(int i=0;i<n;i++)area+=cross(p[i%n],p[(i+1)%n]);
  return area/2;
}

bool isConvex(Polygon p){
  int n=p.size();
  for(int i=0;i<n;i++){
    if(ccw(p[(i+1)%n],p[i%n],p[(i+2)%n])==1)return false;
  }
  return true;
}

// in 2,out 0,on 1
int contains(Polygon g,Point p){
  int n=g.size();
  bool x=false;
  for(int i=0;i<n;i++){
    Vector a=g[i]-p,b=g[(i+1)%n]-p;
    if(abs(cross(a,b))<eps && dot(a,b)<eps)return 1;
    if(a.y>b.y)swap(a,b);
    if(a.y<eps && eps<b.y && cross(a,b)>eps)x=!x;
  }
  if(x)return 2;
  return 0;
}

Polygon convex_hull(Polygon s){
  Polygon g;
  int n=s.size();
  if(n<3)return s;

  sort(s.begin(),s.end());

  for(int i=0;i<n;i++){
    for(int n=g.size();n>=2&&ccw(g[n-2],g[n-1],s[i])==1;n--){
      g.pop_back();
    }
    g.push_back(s[i]);
  }
  for(int i=n-2;i>=0;i--){
    for(int n=g.size();n>=2&&ccw(g[n-2],g[n-1],s[i])==1;n--){
      g.pop_back();
    }
    g.push_back(s[i]);
  }
  reverse(g.begin(),g.end());
  g.pop_back();
  return g;
}

int main()
{
  int n,q,a,b,mi=inf,ii;
  Polygon p,ch;

  cin>>n;
  p.resize(n);
  for(int i=0;i<n;i++)cin>>p[i].x>>p[i].y;

  ch=convex_hull(p);
  int si=ch.size();
  for(int i=0;i<si;i++){
    if(ch[i].y<mi){
      mi=ch[i].y;
      ii=i;
    }
    else if(ch[i].y==mi && ch[i].x<ch[ii].x){
      mi=ch[i].y;
      ii=i;
    }
  }
  cout<<si<<endl;
  for(int i=0;i<si;i++)cout<<ch[(i+ii)%si].x<<" "<<ch[(i+ii)%si].y<<endl;
  
  return 0;
}

Measured memory_bytes: 6156