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

using namespace std;

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;
    }
}a[120001];

int n;
int st[120001], top;
bitset <120001> inhull;

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

bool isLeft(Point a, Point b, Point c) {
    return (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x) > 0;
}

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

void Write()
{
    ofstream fout("infasuratoare.out");
    fout << top - 1 << "\n";
    for (int i = 1; i < top; i++)
        fout << setprecision(6) << fixed << a[st[i]].x << " " << a[st[i]].y << "\n";
}

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