#include <cstdio>
#include <algorithm>
#include <cmath>
#include <fstream>
#include <iomanip>
#define NMAX 120010
#define INF 2000000000
#define EPS 1e-12
using namespace std;

struct pack{
    long double x, y;
    long double u, r;
};
struct pack P[NMAX], S[NMAX];

int n, sol;

void citire ();
void rez ();
void ordoneaza ();
long double pi (struct pack, struct pack, struct pack);
bool comp (struct pack, struct pack);
void afisare();

int main()
{
    citire();
    rez();
    afisare();
    return 0;
}

void citire()
{
    int i;
    ifstream fin ("infasuratoare.in");
    fin>>n;
    for (i=1; i<=n; ++i)
        fin>>P[i].x>>P[i].y;
    /*FILE*fin=fopen ("infasuratoare.in", "r");
    fscanf(fin, "%d", &n);
    for (i=1; i<=n; ++i)
        fscanf(fin, "%lf %lf\n", &P[i].x, &P[i].y);
    fclose(fin);*/
    return;
}

void rez()
{
    int i, vf, prod;
    ordoneaza();
    S[1]=P[1]; S[2]=P[2];
    vf=2;
    for (i=3; i<=n; ++i)
    {
        prod=pi(S[vf-1], S[vf], P[i]);
        while (vf>1 && prod<=0){
                --vf;
                prod=pi(S[vf-1], S[vf], P[i]);
        }
        S[++vf]=P[i];
    }
    sol=vf;
    return;
}

void ordoneaza()
{
    struct pack aux;
    int i, ymin=INF, xmin=INF, minimus;
    for (i=1; i<=n; ++i)
        //if (P[i].x<xmin || (xmin==P[i].x && P[i].y<ymin))
        if (P[i].y<ymin || (ymin==P[i].y && P[i].x<xmin))
            {
                minimus=i;
                ymin=P[i].y;
                xmin=P[i].x;
            }
    aux=P[1];
    P[1]=P[minimus];
    P[minimus]=aux;
    for (i=2; i<=n; ++i)
    {
        if (P[1].x!=P[i].x)
            P[i].u=atan((P[i].y-P[1].y)/(P[i].x-P[1].x));
            else
            P[i].u=INF;
        P[i].r=sqrt((P[i].y-P[1].y)*(P[i].y-P[1].y)+(P[i].x-P[1].x)*(P[i].x-P[1].x));
    }
    sort (P+2, P+n+1, comp);
    return;
}

bool comp (struct pack a, struct pack b)
{
    if(a.u<0&&b.u>=0) return 0;
    if(a.u>=0&&b.u<0) return 1;
    if(a.u!=b.u) return(a.u<b.u);
    return a.r<b.r;
    return a.u<b.u || (a.u==b.u && a.r<b.r);
}

long double pi (struct pack a, struct pack b, struct pack c)
{
    return (b.x-a.x)*(c.y-a.y)-(c.x-a.x)*(b.y-a.y);
}
//returneaza o val. pozitiva daca in b-c se face o intoarcere la stanga
//respectiv o val. negativa daca in b-c se face o intoarcere la dreapta

void afisare()
{
    int i;
    ofstream fout ("infasuratoare.out");
    fout<<sol<<"\n";
    for (i=1; i<=sol; ++i)
        fout<<S[i].x<<" "<<S[i].y<<"\n";
    fout.close();

    //for (i=1; i<=n; ++i)
      //  fout<<setprecision(15)<<P[i].x << " " << P[i].y<<"\n";

    /*FILE*fout=fopen ("infasuratoare.out", "w");
    fprintf(fout, "%d\n", sol);
    for (i=1; i<=sol; ++i)
        fprintf(fout, "%lf %lf\n", S[i].x, S[i].y);

    //for (i=1; i<=n; ++i)
      //  fprintf(fout, "%Lf %Lf\n", P[i].x, P[i].y);
    fclose(fout);*/
    return;
}