#include <stdio.h>
#include <vector>
#include <algorithm>

using namespace std;

FILE* fin, * fout;

struct point {
	float x, y;
};

vector<point> v;
vector<int> poly;

float cross_product(point origin, point a, point b) {
	float x1 = origin.x - a.x;
	float x2 = origin.x - b.x;
	float y1 = origin.y - a.y;
	float y2 = origin.y - b.y;

	return (y2 * x1 - y1 * x2);
}

int side(point origin, point end, point p) {
	float prod = cross_product(origin, end, p);
	if (prod > 0) return 1;
	if (prod < 0) return -1;
	return 0;
}

float dist(point a, point b) {
	float x = a.x - b.x, y = a.y - b.y;
	x *= x;
	y *= y;
	return x + y;
}

void convex_hull() {
	auto cmp = [](point& a, point& b) {return (a.x < b.x || (a.x == b.x && a.y < b.y));};
	sort(v.begin(), v.end(), cmp);
	poly.push_back(0);
	bool done = false;
	int current = 0, next = 1;
	while (!done) {
		for (int i = 0;i < v.size();++i) {
			if (i == current || i == next) continue;
			int s = side(v[current], v[next], v[i]);
			if (s > 0)
				next = i;
			else if (s == 0) {
				if (dist(v[current], v[i]) > dist(v[current], v[next]))
					next = i;
			}
		}
		if (next == 0)
			done = true;
		else {
			poly.push_back(next);
			current = next;
			next = 0;
		}
	}

	fprintf(fout,"%i\n", poly.size());
	for (int i = poly.size() - 1;i >= 0;--i) {
		int j = poly[i];
		fprintf(fout,"%f %f\n", v[j].x, v[j].y);
	}
}

int main() {
	fin = fopen("infasuratoare.in", "r");
	fout = fopen("infasuratoare.out", "w");

	int n;
	fscanf(fin, "%i", &n);
	while (n--) {
		float x, y;
		fscanf(fin, "%f %f", &x, &y);
		v.push_back({ x,y });
	}

	convex_hull();

	return 0;
}