#include<fstream>
#include<string.h>
#include<ctype.h>
#include<iostream>
#include<algorithm>
#include<map>
#include<unordered_map>
#include<array>
#include<deque>
#include<math.h>
#include<functional>
#include<unordered_set>
#include<set>
#include<iomanip>
#include<bitset>
using namespace std;
int n,i,head;
typedef pair<double, double> punct;
punct vec[150150];
punct stiva[150150];
double cross(punct p1, punct p2, punct p3)
{
	return (p2.first - p1.first)*(p3.second - p1.second) - (p2.second - p1.second)*(p3.first-p1.first);
}
bool comp(punct p1, punct p2)
{
	return cross(vec[1], p1, p2)>0;
}
void sort_points()
{
	int pos = 1;
	for (i = 2; i <= n; i++)
		if (vec[i] < vec[pos])
			pos = i;
	swap(vec[1], vec[pos]);
	sort(vec + 2, vec + n + 1,comp);
}
void infasuratoare()
{
	stiva[1] = vec[1];
	stiva[2] = vec[2];
	head = 2;
	for (i = 3; i <= n; i++)
	{
		while (head >= 2 && cross(stiva[head - 1], stiva[head], vec[i]) < 0)
			head--;
		head++;
		stiva[head] = vec[i];
	}
}
int main()
{
	//ifstream f("file.in");
	//ofstream g("file.out");
	ifstream f("infsauratoare.in");
	ofstream g("infasuratoare.out");
	f >> n;
	for (i = 1; i <= n; i++)
	{
		f >> vec[i].first >> vec[i].second;
	}
	sort_points();
	infasuratoare();
	g << fixed;
	g << head << '\n';
	for (i = head; i >= 1; i--)
		g << setprecision(12) << stiva[i].first << " " << stiva[i].second << '\n';
	return 0;
}