#include <fstream>
#include <algorithm>
#include <iomanip>
#define e 0.000000000001
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
int n,i,j,Max,vf;
struct punct
{
    double x,y;
} s[120100],v[120100],aux;
double panta(punct a, punct b, punct c)
{
    return (c.y-a.y)*(b.x-a.x)-(b.y-a.y)*(c.x-a.x);
}
double cmp(punct a,punct b)
{
    return panta(v[1],a,b)<0;
}
double mod(double x)
{
    if (x<0)
    {
        return -x;
    }
    return x ;
}
int main()
{
    fin>>n;
    for(i=1; i<=n; i++)
    {
        fin>>v[i].x>>v[i].y;
        if(v[i].x<v[Max].x || i==1)
        {
            Max=i;
        }
        else
        {
            if(mod(v[Max].x-v[i].x)<e)
                if(v[i].y<v[Max].y)
                {
                    Max=i;
                }
        }
    }
    aux=v[Max];
    v[Max]=v[1];
    v[1]=aux;
    sort(v+2,v+1+n,cmp);
    s[1]=v[1];
    s[2]=v[2];
    vf=2;
    for(i=3; i<=n; i++)
    {
        while(vf>=1 && panta(s[vf-1],s[vf],v[i])>0 )
        {
            vf--;
        }
        vf++;
        s[vf]=v[i];
    }
    fout<<vf<<'\n';
    for(i=vf; i>=1; i--)
        fout<<fixed<<setprecision(6)<<s[i].x<<" "<<s[i].y<<'\n';
    return 0;
}