/* Problem URL: https://cses.fi/problemset/task/2195 */

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

template <class T, class comp = less<>>
using ordered_set = tree<T, null_type , comp , rb_tree_tag , tree_order_statistics_node_update>;

#define V vector

#define rmin(a, b) a = min(a, b)
#define rmax(a, b) a = max(a, b)

#define rep(i, lim) for (int i = 0; i < (lim); i++)
#define nrep(i, s, lim) for (int i = s; i < (lim); i++)

#define repv(i, v) for (auto &i : (v))
#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
#define sortv(v) sort(v.begin(), v.end())
#define all(v) (v).begin(), (v).end()

using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vvvvi = vector<vvvi>;

using ll = long long;

using vl = vector<ll>;
using vvl = vector<vl>;
using vvvl = vector<vvl>;
using vvvvl = vector<vvvl>;

template<class v>
auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
    os << vec[0];
    for (size_t i = 1; i < vec.size(); i++) {
        os << ' ' << vec[i];
    }
    os << '\n';
    return os;
}

template<class v>
auto operator>>(istream &is, vector<v> &vec)->istream& {
    for (auto &i : vec) {
        is >> i;
    }
    return is;
}

template<class v>
auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
    for (auto &i : vec) {
        os << i[0];
        for (size_t j = 1; j < i.size(); j++) {
            os << ' ' << i[j];
        }
        os << '\n';
    }
    return os;
}

template<class v>
auto operator>>(istream  &is, vector<vector<v>> &vec)->istream& {
    for (auto &i : vec) {
        for (auto &j : i) {
            is >> j;
        }
    }
    return is;
}

const int oo = INT32_MAX >> 1;
const ll OO = INT64_MAX >> 1;

struct pt {
    ll x, y;
    
    pt() = default;
    pt(ll x, ll y): x(x), y(y) {}
    pt(const pt &a): x(a.x), y(a.y) {}

    friend istream &operator >> (istream &is, pt &a) {
        is >> a.x >> a.y;
        return is;
    }

    friend ostream &operator << (ostream &os, pt a) {
        os << a.x << ' ' << a.y << '\n';
        return os;
    }

    ll operator ^ (pt b) {
        return x * b.y - y * b.x;
    }

    pt operator - (pt b) {
        return pt(x - b.x, y - b.y);
    }

    bool operator < (pt b) {
        if (x == b.x) {
            return y < b.y;
        }
        return x < b.x;
    }
};

ll sarea2(pt a, pt b, pt c) {
    return (b - a) ^ (c - b);
}

int ccw(pt a, pt b, pt c)
{
    ll ar = sarea2(a, b, c);
    return (ar > 0) - (ar < 0);
}

V<pt> convex_hull(V<pt> v)
{
    sortv(v);
    if (v.size() <= 2) {
        return v;
    }

    int n = v.size();

    V<pt> ac;
    V<pt> tmp;

    rep(i, n) {
        while (ac.size() >= 2 && ccw(ac.end()[-2], ac.end()[-1], v[i]) > 0) {
            ac.pop_back();
        }
        ac.emplace_back(v[i]);
    }

    for (int i = n - 1; i >= 0; i--) {
        while (tmp.size() >= 2 && ccw(tmp.end()[-2], tmp.end()[-1], v[i]) > 0) {
            tmp.pop_back();
        }
        tmp.emplace_back(v[i]);
    }

    ac.pop_back();
    tmp.pop_back();

    repv(i, tmp) {
        ac.emplace_back(i);
    }

    return ac;
}

void pre()
{

}

#define TEST 0

void solve()
{
    int n;
    cin >> n;
    V<pt> a(n);
    cin >> a;
    auto conv = convex_hull(a);
    cout << conv.size() << '\n';
    repv(i, conv) {
        cout << i.x << ' ' << i.y << '\n';
    }
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    pre();

    int t;
    (TEST && cin >> t) || (t = 1);
    while (t--) {
        solve();
    }
}