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

using namespace std;

struct Punct
{
    double x, y;
};
int st[nmax], top;
/// v[i] = 1 daca punctul i este e stiva
Punct a[nmax];
int n;
int v[120005];
///returneaza  < 0 daca punctul a[p] este in semiplanul -
///al dreptei det(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()
{   int i;
    ifstream fin("infasuratoare.in");
    fin >> n;
    for(i = 1; i <= n; i++)
        fin >>a[i].x >> a[i].y;


}

inline bool Comparare(Punct A, 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, Comparare);
    st[++top] = 1;
    st[++top] = 2;
    v[2] = 1;
    for(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(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()
{
    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()
{
    Citire();
    Hill();
    Afisare();

    return 0;
}