#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <vector>
#include <cassert>
#include <cstring>

#define EPS (1e-10)
#define equals(a, b) (fabs((a) - (b)) < EPS)

using namespace std;

static const int COUNTER_CLOCKWISE = 1;
static const int CLOCKWISE = -1;
static const int ONLINE_BACK = 2;
static const int ONLINE_FRONT = -2;
static const int ON_SEGMENT = 0;

struct Point {
    double x, y;
    Point() {}
    Point(double _x, double _y) : x(_x), y(_y) {}

    Point operator + (Point p) { return Point(x+p.x, y+p.y); }
    Point operator - (Point p) { return Point(x-p.x, y-p.y); }
    Point operator * (double a) { return Point(x*a, y*a); }
    Point operator / (double a) { return Point(x/a, y/a); }

    double abs() { return sqrt(norm()); }
    double norm() { return x * x + y * y; }

    bool operator < (const Point &p) const {
        return x != p.x ? x < p.x : y < p.y;
    }

    bool operator == (const Point &p) const {
        return equals(x, p.x) && equals(y, p.y);
    }
};

typedef Point Vector;
typedef vector<Point> Polygon;

struct Segment {
    Point p1, p2;
    Segment(Point _p1 = Point(), Point _p2 = Point()) : p1(_p1), p2(_p2) {}
};

typedef Segment Line;


struct Circle {
    Point c;
    double r;
    Circle(Point _c = Point(), double _r = 0.0) : c(_c), r(_r) {}
};

double dot(Vector a, Vector b) {
    return a.x * b.x + a.y * b.y;
}

double cross(Vector a, Vector b) {
    return a.x * b.y - a.y * b.x;
}

bool isOrthogonal(Vector a, Vector b) {
    return equals(dot(a, b), 0.0);
}

bool isOrthogonal(Point a1, Point a2, Point b1, Point b2) {
    return isOrthogonal(a1-a2, b1-b2);
}

bool isOrthogonal(Segment s1, Segment s2) {
    return equals(dot(s1.p2-s1.p1, s2.p2-s2.p1), 0.0);
}

bool isParallel(Vector a, Vector b) {
    return equals(cross(a, b), 0.0);
}

bool isParallel(Point a1, Point a2, Point b1, Point b2) {
    return isParallel(a1-a2, b1-b2);
}

bool isParallel(Segment s1, Segment s2) {
    return equals(cross(s1.p2-s1.p1, s2.p2-s2.p1), 0.0);
}

Point project(Segment s, Point p) {
    Vector base = s.p2 - s.p1;
    double r = dot(p - s.p1, base) / base.norm();
    return s.p1 + base * r;
}

Point reflect(Segment s, Point p) {
    return p + (project(s, p) - p) * 2.0;
}

Point getCrossPoint(Segment s1, Segment s2) {
    Vector base = s2.p2 - s2.p1;
    double d1 = fabs(cross(base, s1.p1 - s2.p1));
    double d2 = fabs(cross(base, s1.p2 - s2.p1));
    double t = d1 / (d1 + d2);
    return s1.p1 + (s1.p2 - s1.p1) * t;
}

int ccw(Point p0, Point p1, Point p2) {
    Vector a = p1 - p0;
    Vector b = p2 - p0;
    if (cross(a, b) > EPS) return COUNTER_CLOCKWISE;
    if (cross(a, b) < -EPS) return CLOCKWISE;
    if (dot(a, b) < -EPS) return ONLINE_BACK;
    if (a.norm() < b.norm()) return ONLINE_FRONT;

    return ON_SEGMENT;
}

bool intersect(Point p1, Point p2, Point p3, Point p4) {
    return (ccw(p1, p2, p3) * ccw(p1, p2, p4) <= 0 && 
            ccw(p3, p4, p1) * ccw(p3, p4, p2) <= 0);
}

bool intersect(Segment s1, Segment s2) {
    return intersect(s1.p1, s1.p2, s2.p1, s2.p2);
}

double getDistanceLP(Line l, Point p);
bool intersect(Circle c, Line l) {
    double d = getDistanceLP(l, c.c);
    return d < c.r || equals(d, c.r);
}

double getDistance(Point a, Point b);
bool intersect(Circle c1, Circle c2) {
    double d = getDistance(c1.c, c2.c);
    return (d < c1.r + c2.r || (equals(d, c1.r + c2.r)));
}

double getDistance(Point a, Point b) {
    return (a-b).abs();
}

double getDistanceLP(Line l, Point p) {
    return abs(cross(l.p2-l.p1, p-l.p1) / (l.p2-l.p1).abs());
}


double getDistanceSP(Segment s, Point p) {
    if (dot(s.p2-s.p1, p-s.p1) < 0.0) return (p-s.p1).abs();
    if (dot(s.p1-s.p2, p-s.p2) < 0.0) return (p-s.p2).abs();
    return getDistanceLP(s, p);
}

double getDistance(Segment s1, Segment s2) {
    if (intersect(s1, s2)) return 0.0;
    return min(min(getDistanceSP(s1, s2.p1), getDistanceSP(s1, s2.p2)),
            min(getDistanceSP(s2, s1.p1), getDistanceSP(s2, s1.p2)));
}

pair<Point, Point> getCrossPoints(Circle c, Line l) {
    assert(intersect(c, l));
    Vector pr = project(l, c.c);
    Vector e = (l.p2 - l.p1) / (l.p2 - l.p1).abs();
    double base = sqrt(c.r * c.r - (pr - c.c).norm());
    return make_pair(pr + e * base, pr - e * base);
}

double arg(Vector p) { return atan2(p.y, p.x); }
Vector polar(double a, double r) { return Point(cos(r) * a, sin(r) * a); }

pair<Point, Point> getCrossPoints(Circle c1, Circle c2) {
    assert(intersect(c1, c2));
    double d = (c1.c - c2.c).abs();
    double a = acos((c1.r * c1.r + d * d - c2.r * c2.r) / (2 * c1.r * d));
    double t = arg(c2.c - c1.c);
    return make_pair(c1.c + polar(c1.r, t + a), c1.c + polar(c1.r, t - a));
}

int contains(Polygon &g, Point p) {
    int n = g.size();
    bool x = false;
    for (int i = 0; i < n; i++) {
        Point a = g[i] - p, b = g[(i + 1) % n] - p;
        if (fabs(cross(a, b)) < EPS && dot(a, b) < EPS) return 1;
        if (a.y > b.y) swap(a, b);
        if (a.y < EPS && EPS < b.y && cross(a, b) > EPS) x = !x;
    }
    return (x ? 2 : 0);
}

Polygon andrewScan(Polygon s) {
    Polygon u, l;
    if (s.size() < 3) return s;
    sort(s.begin(), s.end());
    u.push_back(s[0]);
    u.push_back(s[1]);
    l.push_back(s[s.size() - 1]);
    l.push_back(s[s.size() - 2]);

    for (int i = 2; i < s.size(); i++) {
        for (int n = u.size(); n >= 2 && ccw(u[n-2], u[n-1], s[i]) == COUNTER_CLOCKWISE; n--) {
            u.pop_back();
        }
        u.push_back(s[i]);
    }
    for (int i = s.size() - 3; i >= 0; i--) {
        for (int n = l.size(); n >= 2 && ccw(l[n-2], l[n-1], s[i]) == COUNTER_CLOCKWISE; n--) {
            l.pop_back();
        }
        l.push_back(s[i]);
    }
    reverse(l.begin(), l.end());
    for (int i = u.size() - 2; i >= 1; i--) l.push_back(u[i]);
    return l;
}


int main() {
    int N;
    scanf("%d", &N);
    Polygon g;
    while (N--) {
        double x, y;
        scanf("%lf %lf", &x, &y);
        g.push_back(Point(x, y));
    }
    Polygon ans = andrewScan(g);
    printf("%lu\n", ans.size());
    int index = 0;
    for (int i = 1; i < ans.size(); i++) {
        if (ans[index].y > ans[i].y) index = i;
        else if (ans[index].y == ans[i].y && ans[index].x > ans[i].x) {
            index = i;
        }
    }
    int t = 0;
    while (t < ans.size()) {
        printf("%d %d\n", (int)ans[index].x, (int)ans[index].y);
        index = (index + 1) % ans.size();
        t++;
    }
    return 0;
}

Measured memory_bytes: 9420