#include <bits/stdc++.h>

using namespace std;
using uint = unsigned int;
using ll = long long;
using ull = unsigned long long;
constexpr ll TEN(int n) { return (n==0) ? 1 : 10*TEN(n-1); }
template<class T> using V = vector<T>;
template<class T> using VV = V<V<T>>;

using D = double;
const D PI = acos(D(-1)), EPS = 1e-10;

int sgn(D a) { return (abs(a) <= EPS) ? 0 : (a < 0 ? -1 : 1); }
int sgn(D a, D b) { return sgn(a-b); }
//relative sign
// int rsgn(D a, D f) {
//     if (abs(a) <= f*EPS) return 0;
//     return (a < 0) ? -1 : 1;
// }
struct Pt2 {
    D x, y;
    Pt2() {}
    Pt2(D _x, D _y) : x(_x), y(_y) {}
    Pt2 operator+(const Pt2 &r) const { return Pt2(x+r.x, y+r.y); }
    Pt2 operator-(const Pt2 &r) const { return Pt2(x-r.x, y-r.y); }
    Pt2 operator*(const Pt2 &r) const { return Pt2(x*r.x-y*r.y, x*r.y+y*r.x); }

    Pt2 operator*(const D &r) const { return Pt2(x*r, y*r); }
    Pt2 operator/(const D &r) const { return Pt2(x/r, y/r); }

    Pt2& operator+=(const Pt2 &r) { return *this=*this+r; }
    Pt2& operator-=(const Pt2 &r) { return *this=*this-r; }
    Pt2& operator*=(const Pt2 &r) { return *this=*this*r; }
    Pt2& operator*=(const D &r) { return *this=*this*r; }
    Pt2& operator/=(const D &r) { return *this=*this/r; }
    
    Pt2 operator-() const { return Pt2(-x, -y); }

    bool operator<(const Pt2 &r) const { return 2*sgn(x, r.x)+sgn(y, r.y)<0; }
    bool operator==(const Pt2 &r) const { return sgn((*this-r).rabs()) == 0; }

    D norm() const { return x*x + y*y; }
    D abs() const { return sqrt(norm()); }
    D rabs() const { return max(std::abs(x), std::abs(y)); } // robust abs
    D arg() const { return atan2(y, x); }

    pair<D, D> to_pair() const { return make_pair(x, y); }
    static Pt2 polar(D le, D th) { return Pt2(le*cos(th), le*sin(th)); }
};
ostream& operator<<(ostream& os, const Pt2 &p) {
    return os << "P(" << p.x << ", " << p.y << ")";
}
using P = Pt2;

D cross(P a, P b) { return a.x*b.y - a.y*b.x; }
D dot(P a, P b) { return a.x*b.x + a.y*b.y; }
// cross(a, b) is too small?
int sgncrs(P a, P b) {
    D cr = cross(a, b);
    if (abs(cr) <= (a.rabs() + b.rabs()) * EPS) return 0;
    return (cr < 0) ? -1 : 1;
}

// -2, -1, 0, 1, 2 : front, clock, on, cclock, back
int ccw(P b, P c) {
    int s = sgncrs(b, c);
    if (s) return s;
    if (!sgn(c.rabs()) || !sgn((c-b).rabs())) return 0;
    if (dot(b, c) < 0) return 2;
    if (dot(-b, c-b) < 0) return -2;
    return 0;
}
int ccw(P a, P b, P c) { return ccw(b-a, c-a); }

using Pol = V<P>;

Pol convex(Pol p) {
    sort(begin(p), end(p));
    p.erase(unique(begin(p), end(p)), end(p));
    if (p.size() <= 2) return p;
    Pol up, dw;
    for (P d: p) {
        size_t n;
        while ((n = up.size()) > 1) {
            if (ccw(up[n-2], up[n-1], d) != 1) break;
            up.pop_back();
        }
        up.push_back(d);
    }
    reverse(begin(up), end(up));
    for (P d: p) {
        size_t n;
        while ((n = dw.size()) > 1) {
            if (ccw(dw[n-2], dw[n-1], d) != -1) break;
            dw.pop_back();
        }
        dw.push_back(d);
    }
    dw.insert(begin(dw), begin(up) + 1, end(up) - 1);
    return dw;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << setprecision(20) << fixed;

    int n;
    cin >> n;
    V<P> p(n);
    for (int i = 0; i < n; i++) {
        D x, y;
        cin >> x >> y;
        p[i] = P(x, y);
    }
    p = convex(p);
    n = int(p.size());
    int s = 0;
    for (int i = 0; i < n; i++) {
        if (p[i].y < p[s].y || (p[i].y == p[s].y && p[i].x < p[s].x)) s = i;
    }
    cout << n << endl;
    for (int i = 0; i < n; i++) {
        P q = p[(s+i)%n];
        cout << int(q.x) << " " << int(q.y) << endl;
    }

    return 0;
}



Measured memory_bytes: 8124