#include <iostream>
#include <cstdio>
#include <vector>
#include <string>
#include <cmath>
#include <algorithm>
#include <memory.h>
#include <stack>
#define pb push_back
#define ll long long
using namespace std;

double pi = acos(-1);

struct point {
    int x, y;
};

int cross(const point &a, const point &b, const point &c) {
    return (b.x - a.x) * (c.y - b.y) - (b.y - a.y) * (c.x - b.x);
}

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

int main() {

    //freopen("convex.in", "r", stdin);
    //freopen("convex.out", "w", stdout);
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    int n;
    cin >> n;
    vector <point> s(n);
    for(int i = 0; i < n; ++i)
        cin >> s[i].x >> s[i].y;
    if(n == 1) {
        cout << "1" << endl;
        cout << s[0].x << " " << s[0].y << endl;
        return 0;
    }
    if(n == 2) {
        if(s[0].x == s[1].x && s[0].y == s[0].y) {
        cout << "1" << endl;
        cout << s[1].x << " " << s[1].y << endl;
        return 0;
        }
    }
    sort(s.begin(), s.end(), cmp);
    point p1 = s[0], p2 = s[s.size() - 1];
    vector <point> up, down;
    up.pb(p1);
    down.pb(p1);

    for(int i = 1; i < n - 1; ++i) {
        if(cross(p1, s[i], p2) < 0) {
            while(up.size() >= 2 && cross(up[up.size() - 2], up[up.size() - 1], s[i]) >= 0)
                up.pop_back();
            up.pb(s[i]);
        }
        else if(cross(p1, s[i], p2) > 0) {
            while(down.size() >= 2 && cross(down[down.size() - 2], down[down.size() - 1], s[i]) <= 0)
                down.pop_back();
            down.pb(s[i]);
        }
    }
    while(up.size() > 2 && cross(up[up.size() - 2], up[up.size() - 1], p2) >= 0)
        up.pop_back();
    up.pb(p2);
    while(down.size() > 2 && cross(down[down.size() - 2], down[down.size() - 1], p2) <= 0)
        down.pop_back();
    down.pb(p2);

    cout << down.size() + up.size() - 2 << endl;
    if(n % 2 == 0) {
       for(int i = up.size() - 1; i >= 0; --i)
            cout << up[i].x << " " << up[i].y << endl;
        for(int i = 1; i < down.size() - 1; ++i)
            cout << down[i].x << " " << down[i].y << endl;
        return 0;
    }
    else {
        for(int i = 0; i < up.size(); ++i)
            cout << up[i].x << " " << up[i].y << endl;;
        for(int i = down.size() - 2; i >= 1; --i)
            cout << down[i].x << " " << down[i].y << endl;
        return 0;
    }
    return 0;
}