#include<bits/stdc++.h>
using namespace std;
ifstream fin ("infasuratoare.in");
ofstream fout("infasuratoare.out");
int n,st[120002],vf;
bool viz[120002];

struct pct
{
    double x,y;
} v[120002];

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

double panta (pct a,pct b,pct c)
{
    return (b.y-a.y)*(c.x-a.x) - (c.y-a.y)*(b.x-a.x);
}

void rez ()
{
    st[1]=1,st[2]=2;
    int i=3,pas=1;
    vf=2;
    while (st[vf]!=1)
    {
        while (viz[i]==1)
        {
            if (i==n)
                pas=-1;
            i=i+pas;
        }
        while (panta(v[st[vf-1]],v[st[vf]],v[i])>0 && vf>=2)
            {
                viz[st[vf]]=0;
                vf--;
            }
        st[++vf]=i;
        viz[i]=1;
    }
}

int main ()
{
    fin>>n;
    int i;
    for (i=1;i<=n;i++)
        fin>>v[i].x>>v[i].y;

    sort(v+1,v+n+1,cmp);

    rez();

    fout<<vf-1<<'\n';
    for (i=2;i<= vf+1;i++)
    {
        fout<<fixed<<setprecision(8)<<v[st[i]].x<<' ';
        fout<<fixed<<setprecision(8)<<v[st[i]].y<<'\n';
    }
    return 0;
}