#include <bits/stdc++.h>
using namespace std;
struct cww{cww(){ios::sync_with_stdio(false);cin.tie(0);}}star;
#define P(x) cout << (x) << "\n"
#define p(x) cout << (x)
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define vv(type, c, m, n, i) vector<vector<type>> c(m, vector<type>(n, i));
#define rep(i,a,n) for(int i=(a), i##_len=(n); i<i##_len; ++i)
#define rrep(i,a,n) for(int i=(a), i##_len=(n); i>i##_len; --i)
#define len(x) ((int)(x).size())
#define mp make_pair
#define eb emplace_back
#define fi first
#define se second
typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector<long long> vll;
typedef vector<string> vs;
typedef vector<bool> vb;
#define EPS (1e-10)
#define equals(a, b) (fabs((a) - (b)) < EPS)
enum CCW { ONLINE_FRONT = -2, CLOCKWISE, ON_SEGMENT, COUNTER_CLOCKWISE, ONLINE_BACK };
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 * (Point p) { return Point(x * p.x, y * p.y); }
	Point operator * (double p) { return Point(x * p, y * p); }
	Point operator / (Point p) { return Point(x / p.x, y / p.y); }
	Point operator / (double p) { return Point(x / p, y / p); }
	void insert(double a, double b) { x = a; y = b; }
	double norm() { return x * x + y * y; }
	double abs() { return sqrt(norm()); }
	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;
	}
};
double abs(Point p) { return sqrt(p.x * p.x + p.y * p.y); }
typedef Point Vector;
struct Circle {
	Point c;
	double r;
	Circle(Point c = Point(), double r = 0.0) : c(c), r(r) {}
};
typedef vector<Point> Polygon;
struct Segment {
	Vector p1, p2;
	Segment(double x1 = 0.0, double y1 = 0.0, double x2 = 0.0, double y2 = 0.0):
		p1(x1, y1), p2(x2, y2) {}
	Segment(Point a1, Point a2) : p1(a1), p2(a2) {}
	void insert(Vector a1, Vector a2) { p1 = a1; p2 = a2; }
};
typedef Segment Line;
inline double dot(Vector a, Vector b) { return a.x * b.x + a.y * b.y; }
inline double cross(Vector a, Vector b) { return a.x * b.y - a.y * b.x; }
inline bool isOrthogonal(Vector a, Vector b) { return equals(dot(a, b), 0.0); }
inline bool isOrthogonal(Vector a1, Vector a2, Vector b1, Vector b2) {
	return isOrthogonal(a1 - a2, b1 - b2);
}
inline bool isOrthogonal(Segment s1, Segment s2) {
	return equals(dot(s1.p2 - s1.p1, s2.p2 - s2.p1), 0.0);
}
inline bool isParallel(Vector a, Vector b) { return equals(cross(a, b), 0.0); }
inline bool isParallel(Vector a1, Vector a2, Vector b1, Vector b2) {
	return isParallel(a1 - a2, b1 - b2);
}
inline bool isParallel(Segment s1, Segment s2) {
	return equals(cross(s1.p2 - s1.p1, s2.p2 - s2.p1), 0.0);
}
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;
}
Point reflect(Segment s, Point p) {
	return p + (project(s, p) - p) * 2.0;
}
int ccw(Point &p0, Point p1, Point p2) {
	Vector a = p1 - p0;
	Vector b = p2 - p0;
	if(cross(a, b) > EPS) return COUNTER_CLOCKWISE;
	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 getDistance(Point &a, Point &b) { return (a - b).abs(); }
double getDistanceLP(Line &l, Point &p) {
	return abs(cross(l.p2 - l.p1, p - l.p1) / (l.p2 - l.p1).abs());
}
double getDistanceSP(Segment &s, Point &p) {
	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 getDistanceLP(s, p);
}
double getDistance(Segment &s1, Segment &s2) {
	if(intersect(s1, s2)) return 0.0;
	return min(min(getDistanceSP(s1, s2.p1), getDistanceSP(s1, s2.p2)),
				min(getDistanceSP(s2, s1.p1), getDistanceSP(s2, s1.p2)));
}
Point getCrossPoint(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;
}
double arg(Vector p) { return atan2(p.y, p.x); }
Vector polar(double a, double r) { return Point(cos(r) * a, sin(r) * a); }
pair<Point, Point> getCrossPoints(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 mp(pr + e * base, pr - e * base);
}
pair<Point, Point> getCrossPoints(Circle c1, Circle c2) {
	double d = (c1.c - c2.c).abs();
	double a = acos((c1.r * c1.r + d * d - c2.r * c2.r) / (2.0 * c1.r * d));
	double t = arg(c2.c - c1.c);
	return mp(c1.c + polar(c1.r, t + a), c1.c + polar(c1.r, t - a));
}
int contains(Polygon g, Point p) {
	int n = len(g);
	bool x = false;
	Point a, b;
	rep(i, 0, n) {
		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);
		if(a.y < EPS && EPS < b.y && cross(a, b) > EPS) x = !x;
	}
	return (x ? 2 : 0);
}
Polygon andrewScan(Polygon s) {
	if(len(s) < 3) return s;
	Polygon u, l;
	sort(all(s), [](const Point& a, const Point& b){return a.y == b.y ? a.x < b.x : a.y < b.y;});
	u.eb(s[0]);
	u.eb(s[1]);
	l.eb(s[len(s) - 1]);
	l.eb(s[len(s) - 2]);
	int _ccw;
	rep(i, 2, len(s)) {
		rrep(n, len(u), 1) {
			_ccw = ccw(u[n - 2], u[n - 1], s[i]);
			if(!(_ccw != CLOCKWISE && _ccw != ONLINE_FRONT)) break;
			u.pop_back();
		}
		u.eb(s[i]);
	}
	rrep(i, len(s) - 3, -1) {
		rrep(n, len(l), 1) {
			_ccw = ccw(l[n - 2], l[n - 1], s[i]);
			if(!(_ccw != CLOCKWISE && _ccw != ONLINE_FRONT)) break;
			l.pop_back();
		}
		l.eb(s[i]);
	}
	reverse(all(l));
	rrep(i, len(u) - 2, 0) l.eb(u[i]);
	return l;
}
int main() {
	cout << setprecision(10) << fixed;
	int n; cin >> n;
	Polygon pg(n);
	rep(i, 0, n) {
		cin >> pg[i].x >> pg[i].y;
	}
	Polygon ans = andrewScan(pg);
	P(len(ans));
	rep(i, 0, len(ans)) {
		cout << int(ans[i].x) << " " << int(ans[i].y) << "\n";
	}
	return 0;
}

Measured memory_bytes: 8124