#include <fstream>
#include<algorithm>
#include<iomanip>
using namespace std;
ifstream cin ("infasuratoare.in");
ofstream cout ("infasuratoare.out");
struct bla
{
    double x,y;
} point[120010];
int viz[120010],st[120010],n,vf=2;
bool sortare (bla q,bla w)
{
    if(q.y!=w.y) return q.y<w.y;
    return q.x<w.x;
}
void read ()
{
    cin>>n;
    for(int i=1;i<=n;i++)
          cin>>point[i].x>>point[i].y;
    sort(point+1,point+1+n,sortare);
}
bool IsOkay (bla a,bla b,bla c)
{
    if((c.x-a.x)*(a.y-b.y)-(a.x-b.x)*(c.y-a.y)<0) return true;
    return false;
}
void convex ()
{
    int next=3,where=1;
    st[1]=1; st[2]=2;  viz[2]=1;
    while(viz[1]==0)
    {
        while(viz[next]!=0)
        {
            if(next==n) where=-1; next+=where;
        }
        while(vf>1 && IsOkay(point[st[vf-1]],point[st[vf]],point[next])) viz[st[vf--]]=0;
        st[++vf]=next; viz[next]=1;
    }
}
void write ()
{
    cout<<vf-1<<"\n";
    for(int i=1;i<vf;++i)
        cout<<fixed<<setprecision(12)<<point[st[i]].x<<" "<<point[st[i]].y<<"\n";
}
int main()
{
    read();
    convex();
    write();
    cin.close();
    cout.close();
    return 0;
}