#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repr(i, n) for (int i = (int)(n); i >= 0; i--)
#define REP(i, m, n) for (int i = (int)(m); i <= (int)(n); i++)
#define REPR(i, m, n) for (int i = (int)(m); i >= (int)(n); i--)
#define all(v) v.begin(), v.end()
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const long long INF = (1LL<<30);

#define EPS (1e-10)
#define equals(a, b) (fabs((a)-(b)) < EPS)

struct Point{
  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 a) { return Point(x*a, y*a); }
  Point operator / (double a) { return Point(x/a, y/a); }

  double abs() { return sqrt(norm()); }
  double norm() { return x*x + y*y; }

  bool operator < (const Point &p) const{
    return x != p.x ? x < p.x : y < p.y;
  }

  bool operator == (const Point &p) const{
    return fabs(x-p.x) < EPS && fabs(y-p.y) < EPS;
  }
};

typedef Point Vector;
typedef vector<Point> Polygon;

struct Segment{
  Point p1, p2;
};

typedef Segment Line;

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

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 a = s.p2 - s.p1;
  Vector b = p - s.p1;
  return s.p1 + a * (dot(a, b)/a.norm());
}

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

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;
  else if(cross(a, b) < -EPS) return CLOCKWISE;
  else if(dot(a, b) < -EPS) return ONLINE_BACK;
  else if(a.norm() < b.norm()) return ONLINE_FRONT;
  else 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 );
}

double getDistance(Point a, Point b){
  Point tmp = a-b;
  return tmp.abs();
}

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

double getDistanceSP(Segment s, Point p){
  Vector a = s.p2 - s.p1;
  Vector b = p - s.p1;
  double n = dot(a, b) / a.norm();
  if(0.0 <= n && n <= 1.0) return getDistanceLP(s, p);
  else return min(getDistance(s.p1, p), getDistance(s.p2, p));
}

double getDistanceSS(Segment s1, Segment s2){
  if(intersect(s1.p1, s1.p2, s2.p1, s2.p2)) return 0.0;
  double res = INF;
  chmin(res, getDistanceSP(s1, s2.p1));
  chmin(res, getDistanceSP(s1, s2.p2));
  chmin(res, getDistanceSP(s2, s1.p1));
  chmin(res, getDistanceSP(s2, s1.p2));
  return res;
}

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

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

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

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

int contains(Polygon g, Point p){
  int n = g.size();
  bool x = false;
  rep(i, n){
    Vector a = g[i] - p;
    Vector 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 && b.y > EPS && cross(a, b) > EPS) x = !x;
  }
  return (x ? 2 : 0);
}

Polygon andrewScan(Polygon s){
  stack<Point> u, l;
  int n = s.size();
  if(n < 3) return s;
  sort(all(s));
  u.push(s[0]);
  u.push(s[1]);
  l.push(s[n-1]);
  l.push(s[n-2]);
  
  REP(i, 2, n-1){
    Point b, bb;
    do{
      b = u.top(); u.pop();
      if(u.empty()) break;
      bb = u.top();
    }while(ccw(b, bb, s[i]) == CLOCKWISE);
    u.push(b);
    u.push(s[i]);
  }

  REPR(i, n-3, 0){
    Point b, bb;
    do{
      b = l.top(); l.pop();
      if(l.empty()) break;
      bb = l.top();
    }while(ccw(b, bb, s[i]) == CLOCKWISE);
    l.push(b);
    l.push(s[i]);
  }

  Polygon res;
  while(!l.empty()){
    res.push_back(l.top());
    l.pop();
  }
  u.pop();
  while(u.size() != 1){
    res.push_back(u.top());
    u.pop();
  }

  return res;
}

int main(){
  int n; cin >> n;
  Polygon s(n);
  rep(i, n){
    int x, y; cin >> x >> y;
    s[i] = Point(x, y);
  }

  Polygon ans = andrewScan(s);
  int m = ans.size();
  int miny = 1001001001;
  int mini = 0;
  rep(i, m){
    int tmp = ans[i].y;
    if(chmin(miny, tmp)) mini = i;
  }
  cout << m << endl;
  rep(i, m){
    cout << ans[(i+mini)%m].x << " " << ans[(i+mini)%m].y << endl;
  }

  return 0;

}






Measured memory_bytes: 8580