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

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

#define Nmax 120001

int n, vf;

struct point
{
    double x, y, a;
}p[Nmax], st[Nmax];

void load()
{
    int istart;
    in >> n;

    p[0].x = INT_MAX;
    p[0].y = INT_MAX;
    for(int i = 1; i <= n; ++ i)
    {
        in >> p[i].x >> p[i].y;

        if(p[i].y < p[0].y)
            p[0] = p[i], istart = i;

        else if(p[i].y == p[0].y)
            if(p[i].x < p[0].x)
                p[0] = p[i], istart = i;
    }

    swap(p[istart], p[1]);
}

void compute_angle()
{
    for(int i = 1; i <= n; ++ i)
        p[i].a = acos((p[i].x - p[0].x) / sqrt(pow(p[i].x - p[0].x, 2) + pow(p[i].y - p[0].y, 2)));
}

bool cmp(point c, point d)
{
    return c.a < d.a;
}

double det(point p1, point p2, point p3)
{
    return p1.x *(p2.y - p3.y) + p2.x *(p3.y - p1.y) + p3.x *(p1.y - p2.y);
}

void hull()
{
    int i = 4;

    st[++ vf] = p[1];
    st[++ vf] = p[2];
    st[++ vf] = p[3];

    while(i <= n)
    {
        if(det(st[vf - 1], st[vf], p[i]) >= 0)
            st[++ vf] = p[i];

        else
        {
            do
            {
                -- vf;
            }
            while(vf >= 1 && det(st[vf - 1], st[vf], p[i]) < 0);

            st[++ vf] = p[i];
        }

        ++ i;
    }
}

void output()
{
    out << vf << '\n';
    for(int i = 1; i <= vf; ++ i)
       {
           out << fixed << setprecision(6) << st[i].x;
           out << ' ';
           out << fixed << setprecision(6) << st[i].y;
           out << '\n';
       }
}

int main()
{
    load();

    compute_angle();

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

    hull();

    output();

    return 0;
}