#include <iostream>
#include <fstream>
#include <algorithm>

#define Lg 120010

using namespace std;

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

int n,start,la,lst = 1, a[Lg], st[Lg];

long double x[Lg], y[Lg];

bool comp(int i,int j)
{
    return (double)(x[i]-x[start])*(y[j]-y[start]) < (double)(x[j]-x[start])*(y[i]-y[start]);
}

long double Semn(int i1,int i2,int i3)
{
    return (long double) x[i1]*y[i2] + x[i2]*y[i3] + x[i3]*y[i1] - y[i1]*x[i2] - y[i2]*x[i3] - y[i3]*x[i1];
}

void citire()
{
    f>>n;
    x[0]=y[0]=0x3f3f3f3f;
    for(int i=1;i<=n;i++)
    {
        f>> x[i] >> y[i];

        if(x[i] < x[start])
            start=i;
        else
            if(x[i] == x[start])
                if(y[i] < y[start])
                    start=i;
    }
}

void ordoneaza()
{
    la=0;
    for(int i=1;i<=n;i++)
    {
        if (i == start) continue;
        a[++la] = i;
    }
    sort(a+1,a+la+1,comp);
}


void formare()
{
    st[lst]=start;
    for(int i=1;i<=la;i++)
    {
        if (a[i] == start) continue;
        while(lst>=2 && Semn(st[lst-1],st[lst],a[i]) > 0)
            lst--;
        st[++lst]=a[i];
    }
    st[++lst]=start;

    reverse(st+1,st+lst+1);

    g << lst-1 << "\n";

    for(int i=1;i<lst;i++)
//        g << st[i] <<" ";
        g << x[st[i]] << " " << y[st[i]] << "\n";

}

int main()
{
    citire();
    ordoneaza();
    formare();

    return 0;
}