#include <bits/stdc++.h>
using namespace std;
#define EPS (1e-10)
#define equals(a, b) (fabs((a) - (b)) < EPS)

class Point {
public:
	double x, y;
	Point(double x = 0.0, double y = 0.0) :
			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);
	}

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

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

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

double dot(Vector v1, Vector v2) {
	return v1.x * v2.x + v1.y * v2.y;
}
double cross(Vector v1, Vector v2) {
	return v1.x * v2.y - v1.y * v2.x;
}
Vector unitVector(Vector v) {
	return v / v.abs();
}
Vector polar(double r, double a) {
	return Vector(r * cos(a), r * sin(a));
}
double arg(Vector v) {
	return atan2(v.y, v.x);
}
bool isOrthogonal(Vector v1, Vector v2) {
	return equals(dot(v1, v2), 0.0);
}
bool isOrthogonal(Segment s1, Segment s2) {
	return equals(dot(s1.p2 - s1.p1, s2.p2 - s2.p1), 0.0);
}
bool isOrthogonal(Point l1, Point l2, Point m1, Point m2) {
	return isOrthogonal(l2 - l1, m2 - m1);
}
bool isParallel(Vector v1, Vector v2) {
	return equals(cross(v1, v2), 0.0);
}
bool isParallel(Segment s1, Segment s2) {
	return equals(cross(s1.p2 - s1.p1, s2.p2 - s2.p1), 0.0);
}
bool isParallel(Point l1, Point l2, Point m1, Point m2) {
	return isParallel(l1 - l2, m1 - m2);
}

enum PositionSP {
	COUNTER_CLOCKWISE = -1,
	CLOCKWISE = 1,
	ONLINE_BACK = 2,
	ONLINE_FRONT = -2,
	ON_SEGMENT = 0
};
PositionSP ccw(Point p1, Point p2, Point p) {
	Vector a = p2 - p1, b = p - p1;
	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);
}
bool intersect(Segment s1, Segment s2) {
	return intersect(s1.p1, s1.p2, s2.p1, s2.p2);
}
Point intersection(Segment s1, Segment s2) {
	double d1 = abs(cross(s2.p2 - s2.p1, s1.p1 - s2.p1));
	double d2 = abs(cross(s2.p1 - s2.p2, s1.p2 - s2.p2));
	return s1.p1 + (s1.p2 - s1.p1) * d1 / (d1 + d2);
}
Point projection(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 distancePP(Point p1, Point p2) {
	return (p1 - p2).abs();
}
double distanceLP(Line l, Point p) {
	return abs(cross(l.p2 - l.p1, p - l.p1) / distancePP(l.p2, l.p1));
}
double distanceSP(Segment s, Point p) {
	if (dot(s.p2 - s.p1, p - s.p1) < 0.0)
		return distancePP(s.p1, p);
	else if (dot(s.p1 - s.p2, p - s.p2) < 0.0)
		return distancePP(s.p2, p);
	else
		return distanceLP(s, p);
}
double distanceSS(Segment s1, Segment s2) {
	if (intersect(s1, s2))
		return 0.0;
	else {
		return min(min(distanceSP(s1, s2.p1), distanceSP(s1, s2.p2)),
				min(distanceSP(s2, s1.p1), distanceSP(s2, s1.p2)));
	}
}

class Circle {
public:
	Point c;
	double r;
	Circle(Point c = Point(), double r = 0.0) :
			c(c), r(r) {
	}
};
pair<Point, Point> intersection(Circle c, Line l) {
	Point pr = projection(l, c.c);
	double base = sqrt(c.r * c.r - (pr - c.c).norm());
	Vector e = unitVector(l.p2 - l.p1);
	return make_pair(pr + e * base, pr - e * base);
}
pair<Point, Point> intersection(Circle c1, Circle c2) {
	double d = (c2.c - c1.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));
}

typedef vector<Point> Polygon;
enum ContainGP {
	OUTSIDE = 0, ON_EDGE = 1, INSIDE = 2
};
ContainGP 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 ON_EDGE;
		if (a.y > b.y)
			swap(a, b);
		if (cross(a, b) > EPS && a.y < EPS && b.y > EPS)
			x = !x;
	}
	return x ? INSIDE : OUTSIDE;
}

Polygon andrewScan(Polygon P) {
	Polygon U, L;
	int n = P.size();
	if (n < 3)
		return P;
	sort(P.begin(), P.end());
	U.push_back(P[0]);
	U.push_back(P[1]);
	for (int i = 2; i < n; i++) {
		while (U.size() >= 2
				&& ccw(U[U.size() - 2], U[U.size() - 1], P[i])
						== COUNTER_CLOCKWISE) {
			U.pop_back();
		}
		U.push_back(P[i]);
	}
	L.push_back(P[n - 1]);
	L.push_back(P[n - 2]);
	for (int i = n - 3; i >= 0; i--) {
		while (L.size() >= 2
				&& ccw(L[L.size() - 2], L[L.size() - 1], P[i])
						== COUNTER_CLOCKWISE) {
			L.pop_back();
		}
		L.push_back(P[i]);
	}
	for (int i = 1; i < L.size() - 1; i++)
		U.push_back(L[i]);
	return U;
}

int main() {
	int N;
	cin >> N;
	Polygon P;
	for (int i = 0; i < N; i++) {
		int x, y;
		cin >> x >> y;
		P.push_back(Point(x, y));
	}
	Polygon C = andrewScan(P);
	cout << C.size() << endl;
	int ind = 0;
	for (int i = 0; i < C.size(); i++) {
		if (C[ind].y > C[i].y || (C[ind].y == C[i].y && C[ind].x > C[i].x)) {
			ind = i;
		}
	}
	int i = ind;
	do {
		cout << C[i].x << " " << C[i].y << endl;
		i--;
		if (i == -1)
			i = C.size() - 1;
	} while (i != ind);
	return 0;
}



Measured memory_bytes: 9284