#include <bits/stdc++.h>
using namespace std;

struct Point {
	double x, y;
	double operator*(const Point&other) {
		return x*other.y - other.x*y;
	}
};

bool comp(Point a, Point b) {
	if(a.x!=b.x) return a.x < b.x;
	return a.y < b.y;
}

bool crease(Point New, Point Origin, Point Old) {
	Old.x = Old.x - Origin.x; Old.y = Old.y - Origin.y;
	New.x = New.x - Origin.x; New.y = New.y - Origin.y;
	return (New*Old) < 0.00;
}

int main() {
	ifstream f("infasuratoare.in");
	ofstream g("infasuratoare.out");
	
	int n; f >> n;
	vector<Point> v(n);
	for(int i=0; i<n; i++) f >> v[i].x >> v[i].y;
	sort(v.begin(), v.end(), comp);
	vector<Point> lower, upper;
	for(int i=0; i<n; i++) {
		while(lower.size() >= 2 and crease(v[i], lower[lower.size()-1], lower[lower.size()-2])) lower.pop_back();
		lower.emplace_back(v[i]);
	}
	for(int i=n-1; i>=0; i--) {
		while(upper.size() >= 2 and crease(v[i], upper[upper.size()-1], upper[upper.size()-2])) upper.pop_back();
		upper.emplace_back(v[i]);
	}
	g << lower.size() + upper.size() - 2 << "\n";
	for(int i=0; i<lower.size()-1; i++) g << fixed << setprecision(12) << lower[i].x << " " << lower[i].y << "\n";
	for(int i=0; i<upper.size()-1; i++) g << fixed << setprecision(12) << upper[i].x << " " << upper[i].y << "\n";
	return 0;
}