#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < n; i++)
#define EPS (1e-10)
#define equals(a, b) (fabs((a) - (b)) < EPS)
const int COUNTER_CLOCKWISE = 1;
const int CLOCKWISE = -1;
const int ONLINE_BACK = 2;
const int ONLINE_FRONT = -2;
const int ON_SEGMENT = 0;

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

  void print()
  {
    printf("%.10f %.10f\n", x, y);
  }

  double arg()
  {
    return atan2(y, x);
  }
};

typedef Point Vector;

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;
}

struct Segment
{
  Point p1, p2;
};

typedef Segment Line;

class Circle
{
public:
  Point c;
  double r;
  Circle(Point c = Point(), double r = 0) : c(c), r(r) {}
};

typedef vector<Point> Polygon;

Point projection(Line l, Point p)
{
  return l.p1 + (l.p2 - l.p1) * (dot(p - l.p1, l.p2 - l.p1) / (l.p2 - l.p1).norm());
}

Point reflection(Line l, Point p)
{
  Point x = projection(l, p);
  return p + (x - p) * 2;
}

int ccw(Point p0, Point p1, Point p2)
{
  Vector a = p1 - p0, 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 is_parallel(Line l1, Line l2)
{
  Vector a = l1.p2 - l1.p1, b = l2.p2 - l2.p1;
  return equals(cross(a, b), 0);
}

bool is_orthogonal(Line l1, Line l2)
{
  Vector a = l1.p2 - l1.p1, b = l2.p2 - l2.p1;
  return equals(dot(a, b), 0);
}

bool intersect(Segment s1, Segment s2)
{
  Point p0 = s1.p1, p1 = s1.p2, p2 = s2.p1, p3 = s2.p2;
  return (ccw(p0, p1, p2) * ccw(p0, p1, p3) <= 0) && (ccw(p2, p3, p0) * ccw(p2, p3, p1) <= 0);
}

Point intersection(Segment s1, Segment s2)
{
  Point p0 = s1.p1, p1 = s1.p2, p2 = s2.p1, p3 = s2.p2;
  double a0 = fabs(cross(p2 - p0, p3 - p0)), a1 = fabs(cross(p2 - p1, p3 - p1));
  return (p0 * a1 + p1 * a0) / (a0 + a1);
}

double line_distance(Line l, Point p)
{
  Point p0 = l.p1, p1 = l.p2;
  return fabs(cross(p1 - p0, p - p0)) / (p1 - p0).abs();
}

double distance(Segment c, Point p)
{
  Point p0 = c.p1, p1 = c.p2;
  if (dot(p1 - p0, p - p0) < -EPS)
  {
    return (p0 - p).abs();
  }
  if (dot(p0 - p1, p - p1) < -EPS)
  {
    return (p1 - p).abs();
  }
  return fabs(cross(p1 - p0, p - p0)) / (p1 - p0).abs();
}

double distance(Segment s1, Segment s2)
{
  if (intersect(s1, s2))
  {
    return 0;
  }
  double res = distance(s1, s2.p1);
  res = min(res, distance(s1, s2.p2));
  res = min(res, distance(s2, s1.p1));
  res = min(res, distance(s2, s1.p2));
  return res;
}

pair<Point, Point> intersection(Circle c, Line l)
{
  Point x = projection(l, c.c);
  double d = line_distance(l, c.c);
  if (equals(d, c.r))
  {
    return make_pair(x, x);
  }
  Point p0 = l.p1, p1 = l.p2;
  Vector u = p1 - p0;
  Vector v = u * (sqrt(c.r * c.r - d * d)) / u.abs();
  Point a0 = x + v, a1 = x - v;
  if (a1 < a0)
  {
    swap(a0, a1);
  }
  return make_pair(a0, a1);
}

Point polar(double r, double a)
{
  return Point{r * cos(a), r * sin(a)};
}

pair<Point, Point> intersection(Circle c1, Circle c2)
{
  double d = (c2.c - c1.c).abs();
  double t = (c2.c - c1.c).arg();
  double a = acos((c1.r * c1.r + d * d - c2.r * c2.r) / (2 * c1.r * d));
  Point a0 = c1.c + polar(c1.r, t + a), a1 = c1.c + polar(c1.r, t - a);
  if (a1 < a0)
  {
    swap(a0, a1);
  }
  return make_pair(a0, a1);
}

int contains(Polygon g, Point p)
{
  int n = g.size();
  bool x = false;
  rep(i, n)
  {
    Vector a = g.at(i) - p, b = g.at((i + 1) % n) - p;
    if (equals(cross(a, b), 0) && dot(a, b) < EPS)
    {
      return 1;
    }
    if (b.y < a.y)
    {
      swap(a, b);
    }
    if (a.y < EPS && b.y > EPS && cross(a, b) > EPS)
    {
      x = !x;
    }
  }
  return x ? 2 : 0;
}

Polygon convex_hull(Polygon s)
{
  if (s.size() < 3)
  {
    if (ccw(s.at(0), s.at(1), s.at(2)) == COUNTER_CLOCKWISE)
    {
      return s;
    }
    else
    {
      reverse(s.begin(), s.end());
      return s;
    }
  }
  sort(s.begin(), s.end());
  Polygon u, l;
  u.push_back(s.at(0));
  u.push_back(s.at(1));
  l.push_back(s.at(s.size() - 1));
  l.push_back(s.at(s.size() - 2));
  for (int i = 2; i < s.size(); i++)
  {
    for (int n = u.size(); n >= 2; n--)
    {
      if (ccw(u.at(n - 2), u.at(n - 1), s.at(i)) != COUNTER_CLOCKWISE)
      {
        break;
      }
      u.pop_back();
    }
    u.push_back(s.at(i));
  }
  for (int i = s.size() - 3; i >= 0; i--)
  {
    for (int n = l.size(); n >= 2; n--)
    {
      if (ccw(l.at(n - 2), l.at(n - 1), s.at(i)) != COUNTER_CLOCKWISE)
      {
        break;
      }
      l.pop_back();
    }
    l.push_back(s.at(i));
  }
  reverse(l.begin(), l.end());
  for (int i = u.size() - 2; i >= 1; i--)
  {
    l.push_back(u.at(i));
  }
  return l;
}

int main()
{
  int n;
  cin >> n;
  Polygon s;
  rep(i, n)
  {
    double x, y;
    cin >> x >> y;
    s.push_back(Point{x, y});
  }
  Polygon p = convex_hull(s);
  int start = 0;
  int m = p.size();
  for (int i = 1; i < m; i++)
  {
    if (p.at(i).y < p.at(start).y)
    {
      start = i;
    }
  }
  cout << m << endl;
  for (int i = start; i < start + m; i++)
  {
    cout << p.at(i % m).x << " " << p.at(i % m).y << endl;
  }
}


Measured memory_bytes: 9332