#include <fstream>
#include <vector>
#include <algorithm>
#include <iomanip>

using namespace std;

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

struct pt {
    double x, y;
};

bool cmp(pt a, pt b) {
    return a.x < b.x || (a.x == b.x && a.y < b.y);
}

bool cw(pt a, pt b, pt c) {
    return a.x*(b.y-c.y)+b.x*(c.y-a.y)+c.x*(a.y-b.y) < 0;
}

bool ccw(pt a, pt b, pt c) {
    return a.x*(b.y-c.y)+b.x*(c.y-a.y)+c.x*(a.y-b.y) > 0;
}

void infasuratoare(vector<pt>& a) {
    if (a.size() == 1)
        return;

    sort(a.begin(), a.end(), &cmp);
    pt p1 = a[0], p2 = a.back();

    vector<pt> up, down;
    up.push_back(p1);
    down.push_back(p1);

    for (int i = 1; i < (int)a.size(); i++) {
        if (i == a.size() - 1 || cw(p1, a[i], p2)) {
            while (up.size() >= 2 && !cw(up[up.size()-2], up[up.size()-1], a[i]))
                up.pop_back();
            up.push_back(a[i]);
        }
        if (i == a.size() - 1 || ccw(p1, a[i], p2)) {
            while(down.size() >= 2 && !ccw(down[down.size()-2], down[down.size()-1], a[i]))
                down.pop_back();
            down.push_back(a[i]);
        }
    }

    a.clear();
    for (int i = 0; i < (int)up.size(); i++)
        a.push_back(up[i]);
    for (int i = down.size() - 2; i > 0; i--)
        a.push_back(down[i]);
}

int main() {
    int n, i;
    pt p;
    vector<pt> v;

    fin >> n;
    for (i = 1; i <= n; i++) {
        fin >> p.x >> p.y;
        v.push_back(p);
    }

    infasuratoare(v);

    fout << fixed << setprecision(6);
    fout << v.size() << '\n';
    for (i = (int)v.size() - 1; i >= 0; i--)
        fout << v[i].x << ' ' << v[i].y << '\n';

    fin.close();
    fout.close();

    return 0;
}