#include <bits/stdc++.h>

using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
struct wow
{
    double x,y;
}v[120005];
int st[120005],n,i,nr,sel[120005];
bool compare (wow a,wow b)
{
    return a.x<b.x||(a.x==b.x&&a.y<b.y);
}
double determinant (wow a,wow b,wow c)
{
    return a.x*b.y+b.x*c.y+a.y*c.x-b.y*c.x-a.y*b.x-a.x*c.y;
}
int main()
{
    f>>n;
    for (i=1;i<=n;i++)
    {
        f>>v[i].x>>v[i].y;
    }
    sort (v+1,v+n+1,compare);
    st[1]=1;
    st[2]=2;
    nr=2;
    for (i=3;i<=n;i++)
    {
        while (nr>1&&determinant(v[st[nr-1]],v[st[nr]],v[i])>=0)
        {
            sel[st[nr]]=0;
            nr--;
        }
        sel[i]=1;
        st[++nr]=i;
    }
    for (i=n;i>=1;i--)
    {
        if (sel[i]==0)
        {
            while (nr>1&&determinant(v[st[nr-1]],v[st[nr]],v[i])>=0)
            {
                sel[st[i]]=0;
                nr--;
            }
            sel[i]=1;
            st[++nr]=i;
        }
    }
   g<<nr-1<<'\n';
   for (i=nr-1;i>=1;i--)
   {
       g<<fixed<<setprecision(6)<<v[st[i]].x<<" "<<v[st[i]].y<<'\n';
   }
   return 0;
}