#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
int k,i,n,x;
struct sor
{
    double x,y;
}v[120001],c[120001];
int ecuatie(double x1,double x2,double x3,double y1,double y2,double y3)
{
    if((x3*y2+x2*y1+x1*y3)>(x1*y2+x2*y3+x3*y1))
        return 1;
    return 0;
}
int cmp(sor A,sor B)
{
    if(A.x==B.x)
        return A.y<B.y;
    else
        return A.x<B.x;
}
int main()
{
    fin>>n;
    for(i=1;i<=n;i++)
        fin>>v[i].x>>v[i].y;
    sort(v+1,v+n+1,cmp);
    c[1].x=v[1].x;c[1].y=v[1].y;
    c[2].x=v[2].x;c[2].y=v[2].y;k=2;
    for(i=3;i<=n;i++)
    {
        k++;
        x=ecuatie(c[k-2].x,c[k-1].x,v[i].x,c[k-2].y,c[k-1].y,v[i].y);
        while(x==0)
        {
            k--;
            x=ecuatie(c[k-2].x,c[k-1].x,v[i].x,c[k-2].y,c[k-1].y,v[i].y);
        }
        c[k].x=v[i].x;
        c[k].y=v[i].y;
    }
    for(i=n;i>0;i--)
    {
        k++;
        x=ecuatie(c[k-2].x,c[k-1].x,v[i].x,c[k-2].y,c[k-1].y,v[i].y);
        while(x==0)
        {
            k--;
            x=ecuatie(c[k-2].x,c[k-1].x,v[i].x,c[k-2].y,c[k-1].y,v[i].y);
        }
        c[k].x=v[i].x;
        c[k].y=v[i].y;
    }
    fout<<k-1<<"\n";
    for(i=k-1;i>0;i--)
        fout<<setprecision(6)<<fixed<<c[i].x<<" "<<c[i].y<<"\n";
    return 0;
}