#include <fstream>
#include <cmath>
#include <algorithm>
#include <iomanip>
#include <utility>

using namespace std;

ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

pair <int,int> x,y;

struct point
{
    double x,y;
}v[120001];

int n,i,k,p,s[120001],t,j;
double eps=1e-12;

inline double det (const point &A, const point &B, const point &C)
{
    return (B.x - A.x) * (C.y - A.y) - (B.y - A.y) * (C.x - A.x);
}

inline bool cmp (const point &A, const point B)
{
    return det (v[1],A,B) < 0;
}

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

    int mini=1;
    for (int i=2; i<=n; ++i)
    {
        if (fabs(v[i].x - v[mini].x) > eps) {if (v[i].x < v[mini].x) mini=i;}
        else if (v[i].y < v[mini].y) mini=i;
    }

    point temp = v[1];
    v[1]=v[mini];
    v[mini]=temp;

    sort (v+2,v+n+1,cmp);

    s[1]=1;
    s[2]=2;
    k=2;

    for (i=3; i<=n; ++i)
    {
        while (k>=2 && det(v[s[k-1]],v[s[k]],v[i]) > 0) k--;
        s[++k]=i;
    }

    fout<<k<<"\n";
    fout<<fixed;
    fout<<v[s[1]].x<<" "<<v[s[1]].y<<"\n";
    for (i=k; i>1; --i) fout<<v[s[i]].x<<" "<<v[s[i]].y<<"\n";

}