#include<iostream>
#include<algorithm>
#include<vector>
#include<stack>
#include<queue>
#include<list>
#include<string>
#include<cstring>
#include<cstdlib>
#include<cstdio>
#include<cmath>
#include<ctime>
using namespace std;

typedef long long ll;

bool debug = false;
const int NIL = -1;
const int INF = 1000000000;
const int NUM = 100010;
const double eps = 1e-10;
clock_t START, END;

int X, Y, E;

//basic defitition
struct Point {
	double x, y;
	Point(double x = 0, double y = 0) :x(x), y(y) {}
};
typedef Point Vector;
Vector operator + (Vector A, Vector B) { return Vector(A.x + B.x, A.y + B.y); }
Vector operator - (Point A, Point B) { return Vector(A.x - B.x, A.y - B.y); }
Vector operator * (Vector A, double p) { return Vector(A.x * p, A.y * p); }
Vector operator / (Vector A, double p) { return Vector(A.x / p, A.y / p); }
bool operator < (const Point& a, const Point& b) { return a.x < b.x || (a.x == b.x && a.y < b.y); }
int dcmp(double x) { if (fabs(x) < eps)return 0; else return x < 0 ? -1 : 1; }
bool operator == (const Point& a, const Point& b) { return dcmp(a.x - b.x) == 0 && dcmp(a.y - b.y) == 0; }
struct Line {
	Point p;
	Vector v;
	Line(Point p, Vector v) :p(p), v(v) {}
	Point point(double t) { return p + v * t; }
	//Line move(double d) { return Line(p + Normal(v) * d, v); }
};
// basic operator
double Dot(Vector A, Vector B) { return A.x * B.x + A.y * B.y; }
double Length(Vector A) { return sqrt(Dot(A, A)); }
double Angle(Vector A, Vector B) { return acos(Dot(A, B) / Length(A) / Length(B)); }
double Cross(Vector A, Vector B) { return A.x * B.y - A.y * B.x; }
double Area2(Point A, Point B, Point C) { return Cross(B - A, C - A); }
Vector Rotate(Vector A, double rad) { return Vector(A.x * cos(rad) - A.y * sin(rad), A.x * sin(rad) + A.y * cos(rad)); }
Vector Normal(Vector A) { double L = Length(A); return Vector(-A.y / L, A.x / L); } //A is not zero vector
//point and line
Point GetLineIntersection(Point P, Vector v, Point Q, Vector w) {
	Vector u = P - Q;
	double t = Cross(w, u) / Cross(v, w);
	return P + v * t;
}//two lines only have one intersection and Cross(v,w) is not zero
double DistanceToLine(Point P, Point A, Point B) {
	Vector v1 = B - A, v2 = P - A;
	return fabs(Cross(v1, v2)) / Length(v1);
}
double DistanceToSegment(Point P, Point A, Point B) {
	if (A == B) return Length(P - A);
	Vector v1 = B - A, v2 = P - A, v3 = P - B;
	if (dcmp(Dot(v1, v2)) < 0) return Length(v2);
	else if (dcmp(Dot(v1, v3)) > 0) return Length(v3);
	else return fabs(Cross(v1, v2)) / Length(v1);
}
Point GetLineProjection(Point P, Point A, Point B) {
	Vector v = B - A;
	return A = v * (Dot(v, P - A) / Dot(v, v));
}
bool SegmentProperIntersection(Point a1, Point a2, Point b1, Point b2) {
	double c1 = Cross(a2 - a1, b1 - a1), c2 = Cross(a2 - a1, b2 - a1), c3 = Cross(b2 - b1, a1 - b1), c4 = Cross(b2 - b1, a2 - b1);
	return dcmp(c1) * dcmp(c2) < 0 && dcmp(c3) * dcmp(c4) < 0;
}
bool OnSegment(Point p, Point a1, Point a2) {
	return dcmp(Cross(a1 - p, a2 - p)) == 0 && dcmp(Dot(a1 - p, a2 - p)) <= 0;
}
double angle(Vector v) { return atan2(v.y, v.x); }
//polygon
typedef vector<Point> Polygon;
double ConvexPolygonArea(Point* p, int n) {
	double area = 0;
	for (int i = 1; i < n - 1; i++)
		area = Cross(p[i] - p[0], p[i + 1] - p[0]);
	return area / 2;
}
int isPointInPolygon(Point p, Polygon& poly) {
	int wn = 0;
	int n = poly.size();
	for (int i = 0; i < n; i++) {
		if (OnSegment(p, poly[i], poly[(i + 1) % n])) return -1;
		int k = dcmp(Cross(poly[(i + 1) % n] - poly[i], p - poly[i]));
		int d1 = dcmp(poly[i].y - p.y);
		int d2 = dcmp(poly[(i + 1) % n].y - p.y);
		if (k > 0 && d1 <= 0 && d2 > 0) wn++;
		if (k < 0 && d2 <= 0 && d1 > 0) wn--;
	}
	if (wn != 0) return 1;
	return 0;
}

bool cmp(Point a, Point b) {
	if (a.x == b.x)
		return a.y < b.y;
	return a.x < b.x;
}

int ConvexHull(vector<Point>& p, int n, vector<Point>& ch) {
	sort(p.begin(), p.end(), cmp);
	int m = 0;
	for (int i = 0; i < n; i++) {
		while (m > 1 && dcmp(Cross(ch[m - 1] - ch[m - 2], p[i] - ch[m - 2])) < 0) {
			m--;
			ch.pop_back();
		}
		ch.push_back(p[i]);
		m++;
	}
	int k = m;
	for (int i = n - 2; i >= 0; i--) {
		while (m > k && dcmp(Cross(ch[m - 1] - ch[m - 2], p[i] - ch[m - 2])) < 0) {
			m--;
			ch.pop_back();
		}
		ch.push_back(p[i]);
		m++;
	}
	if (n > 1) m--;
	return m;
}

int main(void)
{
	if (debug) {
		START = clock();
		freopen("in29.txt", "r", stdin);
		freopen("out.txt", "w", stdout);
	};
	int n, ans;
	double x, y;
	vector<Point> p, ch;
	cin >> n;
	for (int i = 0; i < n; i++) {
		scanf("%lf%lf", &x, &y);
		p.push_back(Point(x, y));
	}
	ans = ConvexHull(p, n, ch);
	ch.pop_back();
	cout << ans << endl;
	int i = 0;
	while (ch[i].y > ch[i + 1].y) {
		ch.push_back(ch[i]);
		i++;
	}
	for (int j = i; j < ans + i; j++)
		printf("%.0lf %.0lf\n", ch[j].x, ch[j].y);
	if (debug) {
		END = clock();
		double endtime = (double)(END - START) / 1000;
		printf("total time = %lf s", endtime);
	}
	return 0;
}


Measured memory_bytes: 7380