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

using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
struct pct{double x, y;} v[120005],st[12005];
double minx, miny;
long long n, i, j, poz,vf;

double aria(pct a, pct b, pct c)
{
    double A=0;
    A=a.x*b.y-b.x*a.y+b.x*c.y-c.x*b.y+c.x*a.y-a.x*c.y;
    return A;
}

bool cmp(pct a, pct b)
{
    if(aria(v[1],a,b)>=0) return true;
    return false;
}

int main()
{
    f>>n;
    for(i=1;i<=n;i++) f>>v[i].x>>v[i].y;
    miny=v[1].y;
    minx=v[1].x;
    poz=1;
    for(i=2;i<=n;i++)
    {
        if(v[i].y<miny || (v[i].y==miny && v[i].x<minx))
        {
            miny=v[i].y;
            minx=v[i].x;
            poz=i;
        }
    }
    swap(v[1],v[poz]);
    sort(v+2,v+n+1,cmp);
    st[1]=v[1];
    st[2]=v[2];
    vf=2;
    v[n+1]=v[1];
    for(i=3;i<=n+1;i++)
    {
        while(vf>=2 && aria(st[vf-1],st[vf],v[i])<0) vf--;
        st[++vf]=v[i];
    }
    g.precision(5);
    g<<vf-1<<'\n';
    for(i=1;i<vf;i++) g<<fixed<<st[i].x<<' '<<st[i].y<<'\n';
    return 0;
}