#include <fstream>
#include<algorithm>
#include<iomanip>
using namespace std;

ifstream cin("infasuratoare.in");
ofstream cout("infasuratoare.out");
int st[120001];
struct punct
{
    double x,y;
    int parte;
}v[120001],p,u;
bool cmp(punct a,punct b)
{
    if(a.x<b.x)
        return true;
    if(a.x>b.x)
        return false;
    if(a.y<b.y)
        return true;
    return false;
}
double arie(punct a, punct b, punct c)
{
    return  a.x*b.y + b.x*c.y + c.x*a.y -b.y*c.x -c.y*a.x - a.y*b.x;
}

int main()
{
    int i,n,ck,k;
    cin>>n;
    for(i=1;i<=n;++i)
    {
        cin>>v[i].x>>v[i].y;
    }
    sort(v+1,v+n+1,cmp);
    p=v[1];
    u=v[n];
    for(i=2;i<=n-1;++i)
    {
        if(arie(p,u,v[i])<0)
            v[i].parte=1;
        else
            v[i].parte=2;
    }
    st[1]=1;
    k=1;
    for(i=2;i<=n;++i)
    {
        if(v[i].parte==1 || v[i].parte==0)
        {
            while(k>1 && arie(v[st[k-1]],v[st[k]],v[i])<0)
                k--;
            k++;
            st[k]=i;
        }
    }
    ck=k;
    st[k]=n;
    for(i=n-1;i>=1;--i)
    {
        if(v[i].parte==2 || v[i].parte==0)
        {
            while(k>ck && arie(v[st[k-1]],v[st[k]],v[i])<0)
                k--;
            k++;
            st[k]=i;
        }
    }
    k--;
    cout<<k<<'\n';
    for(i=1;i<=k;i++)
        cout<<fixed<<setprecision(6)<<v[st[i]].x<<" "<<v[st[i]].y<<" "<<"\n";
    return 0;
}