#include <stdio.h>
#include <algorithm>
#define Nmax 120001
#define inf 0xffffffff

using namespace std;


int h,n=2,poz;
FILE *c,*d;
struct punct
{
    double x, y, p;
} a[Nmax],s[Nmax],z;


bool cmp(punct a,punct b)
{
    if (a.p>b.p)
        return false;
    return true;
}

void citire()
{
	int i;
    z.x=z.y=inf;
    fscanf(c,"%d ",&h);
    for (i=0;i<h;++i)
    {
        fscanf(c,"%lf %lf ",&a[i].x,&a[i].y);
        if(a[i].x<z.x||a[i].x==z.x&&a[i].y<z.y)
        {
            z.x = a[i].x;
            z.y = a[i].y;
            poz = i;
        }
    }
    a[poz]=a[h-1];
    --h;
}

void afisare()
{
	int i;
    fprintf(d,"%d\n",n);
    for (i=0;i<n;++i)
        printf ("%lf %lf\n",s[i].x,s[i].y);
}

void panta()
{
	int i;
    for (i=0;i<h;++i)
        if (a[i].x==z.x)
            a[i].p=inf;
        else
            a[i].p=(a[i].y-z.y)/(a[i].x-z.x);
}

bool determinant(punct a, punct b, punct c)
{
    double det = a.x * b.y + a.y * c.x + b.x * c.y - a.y * b.x - b.y * c.x - c.y * a.x;
    if (det >= 0)
        return 1;
    return 0;
}

void infasuratoare()
{
	int i;
    s[0]=z;
    s[1]=a[0];
    for(i=1;i<h;++i)
        if (determinant(s[n-2],s[n-1],a[i])==1)
            s[n++]=a[i];
        else
        {
            while (determinant(s[n-2],s[n-1],a[i])==0)
                s[--n]=a[i];
            ++n;
        }
}

int main()
{
    c=fopen("infasuratoare.in","r");
	d=fopen("infasuratoare.out","w");
    citire();
    panta();
    sort(a,a+h,cmp);
    infasuratoare();
    afisare();
    return 0;
}