#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>

typedef long long ll;

#define all(x) (x).begin(), (x).end()

using namespace std;

struct pt {
    ll x, y;
    pt() {
        x = 0; y = 0;
    }
    pt(int _x, int _y) {
        x = _x; y = _y;
    }
};

struct vec {
    ll x, y;
    vec(pt p1, pt p2) {
        x = p2.x - p1.x;
        y = p2.y - p1.y;
    }
};

ll sign(ll c) {
    if (c == 0) {
        return c;
    } else {
        return c / abs(c);
    }
}

ostream& operator<<(ostream& out, pt &p) {
    out << p.x << " " << p.y;
    return out;
}

bool operator==(pt p1, pt p2) {
    return p1.x == p2.x && p1.y == p2.y;
}

int operator%(vec v1, vec v2) {
    return sign(v1.x * v2.y - v1.y * v2.x);
}

lb angle(pt p) {
    return atan2(p.y, p.x);
}

bool comp(pt p1, pt p2) {
    ll c = vec(p1, pt()) % vec(p2, pt());
    if (c == 0) {
        return p1.x * p1.x + p1.y * p1.y < p2.x * p2.x + p2.y * p2.y;
    } else {
        return c > 0;
    }
}

int main() {
    int n;
    cin >> n;
    vector<pt> pts(n);
    pt mini(1e9 + 1, 1e9 + 1);
    for (int i = 0; i < n; ++i) {
        cin >> pts[i].x >> pts[i].y;
        if (pts[i].y < mini.y || (pts[i].y == mini.y && pts[i].x < mini.x)) {
            mini = pts[i];
        }
    }
    sort(all(pts), comp);

    vector<pt> ans;
    ans.push_back(mini);
    for (int i = 0; i < n; ++i) {
        if (pts[i] == ans.back() || pts[i] == mini) continue;
        while (ans.size() >= 2 && vec(ans[ans.size() - 1], ans[ans.size() - 2]) % vec(ans[ans.size() - 1], pts[i]) >= 0) {
            ans.pop_back();
        }
        ans.push_back(pts[i]);
    }
    n = ans.size();
    cout << n << '\n';
    for (int i = 0; i < n; ++i) {
        cout << ans[i].x << " " << ans[i].y << '\n';

    }
    return 0;
}