#include <bits/stdc++.h>
#include <iomanip>
using namespace std;
ifstream fin ("infasuratoare.in");
ofstream fout("infasuratoare.out");
struct point
{
    long double x,y;
}v[120010],s[120010];
int f,n,i,ymin=1e9,xmin=1e9,poz;
long double cross_product(point a,point b,point c)
{
    return (b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x);
}
int cmp(point a,point b)
{
    return (cross_product(v[1],a,b)<0);
}
int main()
{
    fin>>n;
    for(i=1;i<=n;i++)
    {
        fin>>v[i].x>>v[i].y;
        if(v[i].y<ymin)
        {
            poz=i;
            xmin=v[i].x;
            ymin=v[i].y;
        }
        else if(v[i].y==ymin && v[i].x<xmin)
        {
            poz=i;
            xmin=v[i].x;
        }
    }
    swap(v[1],v[poz]);
    sort(v+2,v+n+1,cmp);
    s[++f]=v[1];
    s[++f]=v[2];
    for(i=3;i<=n;i++)
    {
        while(f>=2 && cross_product(s[f-1],s[f],v[i])>0)
            f--;
        s[++f]=v[i];
    }
    fout<<f<<'\n';
    fout<<fixed<<setprecision(9);
    for(i=f;i>=1;i--)
        fout<<s[i].x<<" "<<s[i].y<<'\n';
    return 0;
}