#include <bits/stdc++.h>
#define nmax 120012

using namespace std;

struct Punct
{
    double x, y;
};

int st[nmax], top;
Punct a[nmax];
bool v[nmax]; /// Vector de vizite
int n;

/// Ret. < 0 daca punctul a[p] este in semiplanul - al dreptei determinate de punctele (a[i], a[j])
double F(int i, int j, int p)
{
    return  a[p].x * (a[i].y - a[j].y) +
            a[p].y * (a[j].x - a[i].x) +
            a[i].x * a[j].y - a[j].x * a[i].y;

    /**
    * < 0 -> planul -
    * > 0 -> planul +
    * = 0 -> coliniaritate

    Verificare:
    {
        a[1].x = a[1].y = 0;
        a[2].x = a[2].y = 6;
        a[3].x = 7; a[3].y = 7;

        cout << F(1, 2, 3);
    }
    **/
}

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

/// Sortez punctele dupa Y, in caz de egalitate dupa 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;
}

/// Algoritmul lui Hill
void Hill()
{
    int i;

    sort(a + 1, a + n + 1, CMP);

    st[++top] = 1;
    st[++top] = 2;
    v[2] = 1;

    for (i = 3; i <= n; i++)
    {
        /// Scot punctele din semiplanul - al planului format de punctul i actual
        while(top > 1 && F(st[top - 1], st[top], i) < 0)
        {
            v[st[top]] = 0;
            top--;
        }
        st[++top] = i;
        v[i] = 1;
    }

    for (i = n - 1; i >= 1; i--)
        if(v[i] == 0)
        {
            while(top > 1 && F(st[top - 1], st[top], i) < 0)
            {
                v[st[top]] = 0;
                top--;
            }
            st[++top] = i;
            v[i] = 1;
        }
}

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

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