#include <bits/stdc++.h>

using namespace std;

ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");

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

int n, vf;

double delta(point A, point B, point C)
{
	return A.x*B.y + C.x*A.y + B.x*C.y - C.x*B.y - A.x*C.y - B.x*A.y;
}

int compare1(point A, point B)
{
	if(A.x==B.x)
		return (A.y<B.y);
	return (A.x<B.x);
}

int compare2(point B, point C)
{
	return (delta(v[1],B,C) < 0);
}

int i;
int main()
{
	f>>n;
	for(i=1;i<=n;i++)
    {
        f>>v[i].x>>v[i].y;
    }

	sort(v+1,v+n+1,compare1);
	st[1]=v[1];

	sort(v+2,v+n+1,compare2);
	st[2]=v[2];

	vf = 2;

    for(i=3;i<=n;i++)
    {
        while(vf>2 && delta(st[vf-1],st[vf],v[i])>0)vf--;
        vf++;
        st[vf]=v[i];
    }

    g<<vf<<'\n';
    for(i=vf;i>=1;i--)
    {
        g<<fixed<<setprecision(6)<<st[i].x<<" ";
        g<<fixed<<setprecision(6)<<st[i].y<<" ";
        g<<'\n';
    }

	return 0;
}