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

ifstream in("infasuratoare.in");
ofstream out("infasuratoare.out");
int n, i;
int vf, poz, ok;
struct punct
{
    double x, y;
};
punct a[120005];
int stiva[120005];
bool pus[120005];
bool cmp (punct a, punct b)
{
    if(a.x > b.x)
        return false;
    if(a.x == b.x && a.y > b.y)
        return false;
    return true;
}
double determinant (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()
{
    in>>n;
    for(i=1; i<=n; i++)
        in>>a[i].x>>a[i].y;
    sort(a+1, a+n+1, cmp);
    stiva[1]=1;
    stiva[2]=2;
    pus[2]=true;
    vf=2;
    poz=3;
    ok=1;
    while(!pus[1])
    {
        while(pus[poz])
        {
            if(poz==n)
                ok=-1;
            poz+=ok;
        }
        while( vf>=2 && determinant (a[stiva[vf-1]], a[stiva[vf]], a[poz])<0 )
        {
            pus[stiva[vf]]=false;
            vf--;
        }
        vf++;
        stiva[vf]=poz;
        pus[poz]=true;
    }
    out<<vf-1<<'\n';
    out<<setprecision(6)<<fixed;
    for(i=2; i<=vf; i++)
        out<<a[stiva[i]].x<<" "<<a[stiva[i]].y<<'\n';
    return 0;
}