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

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

#define x first
#define y second
#define NMAX 120005

typedef pair<double,double > Point;

Point v[NMAX];
Point s[NMAX];
int n;
int head;

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

inline double cross_product (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 int cmp(const Point& p1,const Point& p2)
{

    return (cross_product(v[1],p1,p2) < 0) ;
}

void sorteaza()
{
    int poz=1;
    for(int i=2;i<=n;i++)
        if(v[i] < v[poz])
            poz = i;

    swap(v[1],v[poz]);

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



}

void infasuratoare()
{
    sorteaza();

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

}

void afisare() {
    fout << fixed;
    fout << head << "\n";
    for (int i = head; i >= 1; --i)
        fout << setprecision(9) << s[i].x << " " << s[i].y << "\n";
}


int main()
{
    citire();

    infasuratoare();

    afisare();

    return 0;
}