#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
struct el{double x; double y;};
el a[120001],aa,st[120001];
int n,i,poz;
struct mm{double x; double y;};
double xx,yy,minix,miniy;
double calc(int n)
{
    return (a[n].y-a[n].x)/(a[1].y-a[1].x);
}
double cal(el aa, el b, el c)
{
    return (b.x-aa.x)*(c.y-aa.y)-(b.y-aa.y)*(c.x-aa.x);
}
int cmp(el &aa, el& bb)
{
    double ads=cal(a[1],aa,bb);
   return ads< 0;
}

int main()
{
    f>>n;
    f>>minix>>miniy;
    a[1].x=minix;
    a[1].y=miniy;
    for(i=2;i<=n;i++)
    {
        f>>xx>>yy;
        a[i].x=xx;
        a[i].y=yy;
        if(a[i].x<minix)
        {
            minix=a[i].x;
            miniy=a[i].y;
            poz=i;
        }
        else
            if(a[i].x==minix and a[i].y<miniy)
        {
            miniy=a[i].y;
            poz=i;
        }
    }
    aa=a[poz];
    a[poz]=a[1];
    a[1]=aa;

    sort(a+2,a+n+1,cmp);
    st[1].x=a[1].x;
    st[1].y=a[1].y;
    st[2].x=a[2].x;
    st[2].y=a[2].y;
    int s=2;
    for(i=3;i<=n;i++)
    {

        while(s>=2 and cal(st[s],st[s-1],a[i])<0)
            s--;
        s++;
        st[s].x=a[i].x;
        st[s].y=a[i].y;
    }
    g<<s<<'\n';
    for(i=s;i>=1;i--)
        g<<fixed<<setprecision(9)<<st[i].x<<" "<<st[i].y<<'\n';
    return 0;
}