#include <bits/stdc++.h>

using namespace std;

ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

#define x first
#define y second

using Point = pair<double, double>;

const int NMAX = 12e4;

int N;
Point points[NMAX + 1];
vector<Point> st;

double det(const Point &A, const Point &B, const Point &C) {
	return (B.x - A.x) * (C.y - A.y) - (B.y - A.y) * (C.x - A.x);
}

void sortPoints() {
	int pos = 1;
	for(int i = 2; i <= N; i++) {
		if(points[i] < points[pos]) {
			pos = i;
		}
	}

	swap(points[1], points[pos]);
	sort(points + 2, points + N + 1, [] (const Point &A, const Point &B) {
		return det(points[1], A, B) < 0;
	});

	// for(int i = 1; i <= N; i++) {
	// 	cout << points[i].first << " " << points[i].second << '\n';
	// }
}

void grahamScan() {
	sortPoints();

	st.push_back(points[1]);
	st.push_back(points[2]);

	for(int i = 3; i <= N; i++) {
		while(st.size() >= 2 && det(st[st.size() - 2], st[st.size() - 1], points[i]) > 0) {
			st.pop_back();
		}
		st.push_back(points[i]);
	}
}

int main() {
	fin >> N;

	for(int i = 1; i <= N; i++) {
		double x, y;
		fin >> x >> y;

		points[i] = Point(x, y);
	}

	grahamScan();

	fout << st.size() << '\n';
	for(const auto &it: st) {
		fout << fixed << setprecision(9) << it.first << " " << it.second << '\n';
	}
	return 0;
}