#include <iostream>
#include <string>
#include <stack>
#include <queue>
#include <vector>
#include <list>
#include <set>
#include <map>
#include <algorithm>
#include <cmath>

#include <cstdio>

using namespace std;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define repc(i, s, n) for (int i = (s); i <= (n); i++)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; i--)
#define rrepc(i, s, n) for (int i = (s); i >= (n); i--)
#define swap(a, b, type) { type _tmp = a; a = b; b = _tmp; }
typedef long long ll;
typedef unsigned long long ull;

/*================================================
	Geometry
================================================*/
#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 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;
struct Segment { Point p1, p2; };
typedef Segment Line;
class Circle {
public:
	Point c;
	double r;
	Circle(Point c = Point(), double r = 0.0) : c(c), r(r) {}
};
typedef vector<Point> Polygon;

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; }

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); }

double Distance_PP(Point a, Point b) { return (a - b).abs(); }
double Distance_PL(Point p, Line l) { return abs(cross(l.p2 - l.p1, p - l.p1)) / (l.p2 - l.p1).abs(); }
double Distance_PS(Point p, Segment s) {
	if (dot(s.p2 - s.p1, p - s.p1) < 0.0) return (p - s.p1).abs();
	if (dot(s.p1 - s.p2, p - s.p2) < 0.0) return (p - s.p2).abs();
	return Distance_PL(p, s);
}
double Distance_SS(Segment s1, Segment s2) {
	double op1, op2, op3, op4, distance;

	if (intersect(s1, s2)) return 0.0;

	op1 = Distance_PS(s1.p1, s2);
	op2 = Distance_PS(s1.p2, s2);
	op3 = Distance_PS(s2.p1, s1);
	op4 = Distance_PS(s2.p2, s1);

	distance = min(op1, op2);
	distance = min(distance, op3);
	distance = min(distance, op4);

	return distance;
}
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;
}
double arg(Vector p) { return atan2(p.y, p.x); }
Vector polar(double a, double r) { return Point(cos(r) * a, sin(r) * a); }
Point CrossPoint(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;
}
pair<Point, Point> CrossPoint(Circle c, Line l) {
	Vector pr = project(l, c.c);
	Vector e = (l.p2 - l.p1) / (l.p2 - l.p1).abs();
	double base = sqrt(c.r * c.r - (pr - c.c).norm());
	return make_pair(pr + e * base, pr - e * base);
}
pair<Point, Point> CrossPoint(Circle c1, Circle c2) {
	double d = (c1.c - c2.c).abs();
	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 make_pair(c1.c + polar(c1.r, t + a), c1.c + polar(c1.r, t - a));
}
int contains(Polygon g, Point p) {
	/* IN: 2, ON: 1, OUT: 0 */
	int n = g.size();
	bool x = false;
	rep(i, n) {
		Point 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, Point);
		if (a.y < EPS && EPS < b.y && cross(a, b) > EPS) x = !x;
	}
	return (x ? 2 : 0);
}
Polygon andrewScan(Polygon s){
	/* 凸包の辺上の点を含めない場合、"== COUNTER_CLOCKWISE" を "!= CLOCKWISE" に置き換える。 */
	Polygon u, l;
	if (s.size() < 3) return s;
	sort(s.begin(), s.end());
	u.push_back(s[0]);
	u.push_back(s[1]);
	l.push_back(s[s.size() - 1]);
	l.push_back(s[s.size() - 2]);

	repc(i, 2, s.size() - 1) {
		for (int n = u.size(); n >= 2 && ccw(u[n - 2], u[n - 1], s[i]) == COUNTER_CLOCKWISE; n--) {
			u.pop_back();
		}
		u.push_back(s[i]);
	}

	rrepc(i, s.size() - 3, 0) {
		for (int n = l.size(); n >= 2 && ccw(l[n - 2], l[n - 1], s[i]) == COUNTER_CLOCKWISE; n--) {
			l.pop_back();
		}
		l.push_back(s[i]);
	}

	reverse(l.begin(), l.end());
	rrepc(i, u.size() - 2, 1) l.push_back(u[i]);

	return l;
}

int main()
{
	int n, sIndex;
	Point p, sPoint;
	Polygon g, ans;

	cin >> n;
	rep(i, n) {
		cin >> p.x >> p.y;
		g.push_back(p);
	}

	ans = andrewScan(g);

	sPoint.x = 200000;
	sPoint.y = 200000;
	rep(i, ans.size()) {
		if (ans[i].y < sPoint.y) {
			sIndex = i;
			sPoint = ans[i];
		}
		else if (equals(ans[i].y, sPoint.y) && ans[i].x < sPoint.x) {
			sIndex = i;
			sPoint = ans[i];
		}
	}

	cout << ans.size() << endl;
	rep(i, ans.size()) {
		printf("%d %d\n", (int)ans[sIndex].x, (int)ans[sIndex].y);
		sIndex = (sIndex + 1) % ans.size();
	}

	return 0;
}


Measured memory_bytes: 10384