#include <bits/stdc++.h>

using namespace std;

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

const int Nmax = 120005;

int n, top;
int st[Nmax];
bool viz[Nmax]; /// viz[i] = true => punctul i se afla in infasuratorare convexa

struct Punct
{
    double x, y;
};
Punct a[Nmax];

/// Sortez crescator dupa coordonata y  si in caz de egalitate crescator dupa coordonata x
inline bool CMP(const Punct A, const Punct B)
{
    if(A.y == B.y) return A.x < B.x;
    return A.y < B.y;
}

/// verific in ce cadran se afla punctul cu numarul k fata de dreapta determinata de punctele cu numarul i respectiv j
/// 0 = sunt coliniatre , > 0 se afla in cadranul + , < 0 se afla in cadranul -
inline double CHECK(int i, int j, int k)
{
    ///return (a[i].x * a[j].y + a[i].y * a[k].x + a[j].x * a[k].y - a[k].x * a[j].y - a[j].x * a[i].y - a[i].x * a[k].y);
    return (a[i].x - a[k].x) * (a[j].y - a[k].y) - (a[j].x - a[k].x) * (a[i].y - a[k].y);
}

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

inline void Do()
{
    int i;
    sort(a + 1, a + n + 1, CMP);
    st[++top] = 1;
    st[++top] = 2;
    viz[top] = 2;
    for (i = 3 ; i <= n ; i++)
    {
        while(top > 1 && CHECK(st[top - 1], st[top], i) < 0)
        {
            viz[st[top]] = false;
            top--;
        }
        st[++top] = i;
        viz[i] = true;
    }
    for(i = n ; i >= 1 ; i--)
        if(!viz[i]) /// nu se afla in infasuratoare
        {
            while(top > 1 && CHECK(st[top - 1], st[top], i) < 0)
            {
                viz[st[top]] = false;
                top--;
            }
            st[++top] = i;
            viz[i] = true;
        }
}

void Write()
{
    int i;
    fout << top - 1 << "\n";
    for(i = 1 ; i < top ; i++)
        fout << fixed << setprecision(12) << a[st[i]].x << " " << a[st[i]].y << "\n";
    fout.close();
}

int main()
{
    Read();
    Do();
    Write();
    return 0;
}