#include <bits/stdc++.h>

using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
struct nani
{
    double x,y;
}v[120005];
int s[120005],sel[120005];
int compare (nani a,nani b)
{
    return a.x<b.x||(a.x==b.x&&a.y<b.y);
}
long long det(nani a,nani b,nani c)
{
    return (a.x*b.y)+b.x*c.y+a.y*c.x-b.y*c.x-a.y*b.x-c.y*a.x;
}
int n,i,k;
int main()
{
    f>>n;
    for (i=1;i<=n;i++)
    {
        f>>v[i].x>>v[i].y;
    }
    sort (v+1,v+n+1,compare);
    s[1]=1;
    s[2]=2;
    k=2;
    for (i=3;i<=n;i++)
    {
        while (k>1&&det(v[s[k-1]],v[s[k]],v[i])>=0)
        {
            sel[s[k]]=0;
            k--;
        }
        sel[i]=1;
        s[++k]=i;
    }
    for (i=n;i>=1;i--)
    {
        if (sel[i]==0)
        {
           while (k>1&&det(v[s[k-1]],v[s[k]],v[i])>=0)
        {
            sel[s[k]]=0;
            k--;
        }
        sel[i]=1;
        s[++k]=i;
        }
    }
    g<<k-1<<'\n';
    for (i=k-1;i>=1;i--)
    {
        g<<fixed<<setprecision(6)<<v[s[i]].x<<" "<<fixed<<setprecision(6)<<v[s[i]].y<<'\n';
    }
    return 0;
}