#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

struct Point {
	double x,y;
};

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

int cross(Point o, Point a, Point b) {
	return (a.x-o.x)*(b.y-o.y) - (a.y-o.y)*(b.x-o.x);
}

int main() {
	ifstream in("infasuratoare.in");
	unsigned n;
	in >> n;

	vector<Point> points(n);

	for(Point &p:points) {
		in >> p.x >> p.y;
	}

	sort(points.begin(), points.end());

	vector<Point> top;

	for(unsigned i = 0; i < points.size(); ++i) {
		while(top.size() >= 2 && cross(*(top.end()-2),*(top.end()-1),points[i]) <= 0) {
			top.pop_back();
		}
		top.push_back(points[i]);
	}
	top.pop_back();

	vector<Point> bottom;
	for(int i = points.size()-1; i >= 0; --i) {
		while(bottom.size() >= 2 && cross(*(bottom.end()-2),*(bottom.end()-1),points[i]) <= 0) {
			bottom.pop_back();
		}
		bottom.push_back(points[i]);
	}
	bottom.pop_back();


	ofstream out("infasuratoare.out");
	out << top.size() + bottom.size() << '\n';
	for(Point p:top) {
		out << p.x << ' ' << p.y << '\n';
	}
	for(Point p:bottom) {
		out << p.x << ' ' << p.y << '\n';
	}

	return 0;
}