#include <bits/stdc++.h>

using namespace std;

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

const int DIM = 12e4 + 1;

struct Point
{
	long double x, y;
};

Point v[DIM];
Point st[DIM];

long double trigo(Point A, Point B, Point C)
{
	return ((B.y - A.y) * (C.x - A.x) - (C.y - A.y) * (B.x - A.x));
}

bool cmp(Point A, Point B)
{
	return (trigo(v[1], A, B) > 0);
}

main()
{
	int n;
	fin >> n;
	
	int start = 0;
	
	for(int i = 1; i <= n; ++i)
	{
		fin >> v[i].x >> v[i].y;
		
		if(start == 0 || v[i].x < v[start].x || (v[i].x == v[start].x && v[i].y < v[start].y))
			start = i;
	}
	
	swap(v[start], v[1]);
	
	sort(v + 2, v + n + 1, cmp);
	
	st[1] = v[1];
	st[2] = v[2];
	
	int k = 2;
	
	for(int i = 3; i <= n; ++i)
	{
		while(k >= 2 && trigo(st[k - 1], st[k], v[i]) < 0)
			--k;
		
		st[++k] = v[i];
	}
	
	fout << k << '\n';
	
	for(int i = k; i >= 1; --i)
	{
		fout << fixed << setprecision(7) << st[i].x << ' ' << st[i].y << '\n';
	}
}