#include <bits/stdc++.h>
#define MOD 1000000007
using namespace std;

ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");

struct elem
{
    double x,y;
};

elem v[120001];
int st[120001],viz[120001];

inline bool cmp(const elem &a, const elem &b)
{
    if(a.x==b.x) return a.y<b.y;
    return a.x<b.x;
}

bool panta(elem a, elem b, elem c)
{
    return(c.y-a.y)*(b.x-a.x)<=(b.y-a.y)*(c.x-a.x);
}


int main()
{int i,n,vf,pas=1;
    f>>n;
    for (i=1;i<=n;i++)
        f>>v[i].x>>v[i].y;
    sort(v+1,v+n+1,cmp);
    st[1]=1;
    st[2]=2;
    vf=2;
    viz[2]=1;
    i=3;
    while (viz[1]==0)
    {   if (viz[i]==0)
        {
            while (vf>1 && panta(v[st[vf-1]],v[st[vf]],v[i])==1)
            {
                viz[st[vf]]=0;
                vf--;
            }
            vf++;
            st[vf]=i;
            viz[i]=1;
        }
        if (i==n) pas=-1;
        i+=pas;
    }
    vf--;
    g<<vf<<'\n';
    for (i=1;i<=vf;i++)
        g<<fixed<<setprecision(12)<<v[st[i]].x<<' '<<fixed<<setprecision(12)<<v[st[i]].y<<'\n';
}