#include<fstream>
#include<algorithm>
#include<iomanip>
#define DIM 120100
using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
int i,n,s[DIM],k;
bool viz[DIM];
struct el
{
    float x,y;
    
}v[DIM];
double cm(el A,el B)
{
    if(A.x!=B.x)
    return A.x>B.x;
    return A.y<B.y;
}
double det(int i,int j,int k)
{
    double D;
    D=v[i].x*v[j].y+v[j].x*v[k].y+v[i].y*v[k].x-v[i].y*v[j].x-v[j].y*v[k].x-v[i].x*v[k].y;
    return D;
}
int main ()
{
    f>>n;
    for(i=1;i<=n;++i)
    f>>v[i].x>>v[i].y;
    sort(v+1,v+n+1,cm);
    viz[2]=1;
    s[1]=1; s[2]=2;
    k=2;
    for(i=3;i<=n;++i)
    {
        if(det(s[k-1],s[k],i)<0)
        {
        s[++k]=i; viz[i]=1;
        }
        else
        {
            while(det(s[k-1],s[k],i)>=0&&k>1)
            { viz[s[k]]=0; s[k]=0; k--; }
            s[++k]=i;
            viz[i]=1;
        }
    }
    for(i=n-1;i>=1;--i)
    {
        if(!viz[i])
        if(det(s[k-1],s[k],i)<0)
        {
            s[++k]=i; viz[i]=1;
        }
        else
        {
            while(det(s[k-1],s[k],i)>=0&&k>1)
            { viz[s[k]]=0; s[k]=0; k--; }
            s[++k]=i;
            viz[i]=1;
        }
    }
    g<<k-1<<"\n";
    
    k--;
    for(i=k-1;i>=1;--i)
        g<<fixed<<setprecision(6)<<v[s[i]].x<<" "<<v[s[i]].y<<"\n";
	g<<v[s[k]].x<<" "<<v[s[k]].y<<"\n";
    return 0;
}