#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
struct punct {double x; double y;} p[120005],s[120005],a,b,c;
int n,j,k;
double determinant(punct a, punct b, punct c)
{
    return a.x*b.y+a.y*c.x+b.x*c.y-b.y*c.x-a.x*c.y-a.y*b.x;
}
bool comp(punct i, punct j)
{
    double d;
    d=determinant(p[1],i,j);
    if(d>0) return true;
    else return false;
}
int main()
{
    //Punem pe pozitia 1 a vectorului p cel mai din stanga-jos punct
    fin>>n;
    fin>>p[1].x>>p[1].y;
    j=1;
    for(int i=2;i<=n;i++)
    {
        fin>>p[i].x>>p[i].y;
        if(p[i].x<p[j].x||((p[i].x==p[j].x)&&(p[i].y<p[j].y))) j=i;
    }
    swap(p[1],p[j]);
    //Sortam punctele dupa polaritate
    sort(p+2,p+n+1,comp);
    //Punem punctele in stiva
    s[1]=p[1]; s[2]=p[2];s[3]=p[3];
    k=3;
    for(int i=4;i<=n;i++)
    {
        while(determinant(s[k-1],s[k],p[i])<0)k--;
        s[++k]=p[i];
    }
    fout<<k<<'\n';
    fout<<fixed;
    for(int i=1;i<=k;i++)
    {
        fout<<setprecision(6)<<s[i].x<<' '<<setprecision(6)<<s[i].y<<'\n';
    }
    return 0;
}