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

using namespace std;

ifstream cin("infasuratoare.in");
ofstream cout("infasuratoare.out");

struct POINT {
	double x, y;
} point[120100];

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

vector <POINT> down;
vector <POINT> up;

double det(POINT a, POINT b, POINT c) {
	return a.x * b.y + b.x * c.y + c.x * a.y - a.y * b.x - b.y * c.x - c.y * a.x;
}

int main() {

	ios::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);

	int n;
	cin >> n;

	for (int i = 1; i <= n; i++) {
		cin >> point[i].x >> point[i].y;
	}

	sort(point + 1, point + n + 1, cmp);

	for (int i = 1; i <= n; i++) {

		while (down.size() > 1 && det(down[down.size() - 2], down[down.size() - 1], point[i]) <= 0) {
			down.pop_back();
		}
		down.push_back(point[i]);
	}

	for (int i = n; i >= 1; i--) {

		while (up.size() > 1 && det(up[up.size() - 2], up[up.size() - 1], point[i]) <= 0) {
			up.pop_back();
		}
		up.push_back(point[i]);
	}

	cout << down.size() + up.size() - 2 << '\n';

	for (int i = 0; i < down.size() - 1; i++) {
		cout << setprecision(12) << fixed << down[i].x << " " << down[i].y << '\n';
	}

	for (int i = 0; i < up.size() - 1; i++) {
		cout << setprecision(12) << fixed << up[i].x << " " << up[i].y << '\n';
	}

	return 0;
}