#include <bits/stdc++.h>
#define nmax 120003

using namespace std;

struct Punct
{
    double x, y;
};

Punct a[nmax];
int n;
int st[nmax], top;
int v[nmax]; /// v[i] = 1 daca a[i] este pe stiva;

/**
    Ret. < 0 daca punctul a[p]
    este in semiplanul - al dreptei det. depunctele (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;
}

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

inline bool Compara(Punct A, Punct B)
{
    if (A.y == B.y) return (A.x < B.x);
    return A.y < B.y;
}

/// Alg. lui Hill:
void Hill()
{
    sort(a + 1, a + n + 1, Compara);
    st[++top] = 1;
    st[++top] = 2;
    v[2] = 1;

    for(int i = 3; i <= n; i++)
    {
        while(top > 1 && F(st[top - 1], st[top], i) < 0)
        {
            v[st[top]] = 0;
            top--;
        }
        st[++top] = i;
        v[i] = 1;
    }
    for(int i = n - 1; i >= 1; i--)
    {
        if (v[i] == 0)
        {
            while(F(st[top - 1], st[top], i) < 0)
             {
                  v[st[top]] = 0;
                  top--;
             }
           st[++top] = i;
           v[i] = 1;
        }
    }
}

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

int main()
{
    Citire();
    Hill();
    Afisare();
    return 0;
}