#include <fstream>
#include <iostream>
#include <stack>
#include <algorithm>
#include <bitset>
#include <iomanip>

using namespace std;

const int N = 120005;

struct Point
{
    double x, y;
    bool operator < (const Point other) const
    {
        if (this -> y == other.y) return (this -> x < other.x);
        return (this -> y < other.y);
    }
};

Point a[N];
int n, st[N], top;
bitset <N> inhull;

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

double Check_Plane (Point A, Point B, Point C) ///Point C in relation to line AB
{
    return A.y * (C.x - B.x) + C.y * (B.x - A.x) + B.y * (A.x - C.x);
}

void Convex_Hull ()
{
    sort(a + 1, a + n + 1);
    top = 2;
    st[1] = 1;
    st[2] = 2;
    inhull[1] = inhull[2] = 1;
    for (int i = 3; i <= n; i++)
    {
        while (top > 1 && Check_Plane(a[st[top - 1]], a[st[top]], a[i]) < 0)
        {
            inhull[st[top]] = 0;
            top--;
        }
        st[++top] = i;
        inhull[i] = 1;

    }
    inhull[1] = 0;
    for (int i = n; i >= 1; i--)
    {
        if (!inhull[i])
        {
            while (top > 1 && Check_Plane(a[st[top - 1]], a[st[top]], a[i]) < 0)
            {
                inhull[st[top]] = 0;
                top--;
            }
            st[++top] = i;
            inhull[i] = 1;
        }
    }
    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";
    fout.close();
}

int main()
{
    Read();
    Convex_Hull();
    return 0;
}