#include <iostream>
#include <cmath>
#include <algorithm>
#include <vector>
#include <iomanip>
using namespace std;
#define EPS (1e-10)
#define equals(a, b) (fabs((a) - (b)) < EPS)
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;

class Point {
    public:
    double x, y;

    Point(double x = 0, double y = 0): 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 norm() { return x * x + y * y; }
    double abs() { return sqrt(norm()); }

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

    bool operator == (const Point &p) const {
        return fabs(x - p.x) < EPS && fabs(y - p.y) < EPS;
    }
};

struct Segment {
    Point p1, p2;
};

class Circle {
    public:
    Point c;
    double r;
    Circle(Point c = Point(), double r = 0.0): c(c), r(r) {}
};

typedef vector<Point> Polygon;
typedef Point Vector;
typedef Segment Line;

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;
}

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

double getDistanceLP(Line l, Point p) {
    return fabs(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);
}

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 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)));
}

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

pair<Point, Point> getCrossPoints(Circle c, Line 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) {
    double d = (c2.c - c1.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 );
}

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

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]) > 0; --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]) > 0; --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, index;
    double x, y;
    Polygon g, t;
    cin >> n;
    for (int i = 0; i != n; ++i)
    {
        cin >> x >> y;
        g.push_back(Point(x, y));
    }
    g = andrewScan(g);
    t = g;
    sort(t.begin(), t.end(), cmp);
    for (int i = 0; i != g.size(); ++i)
    {
        if (g[i] == t[0])
        {
            index = i;
        }
    }
    cout << g.size() << endl;
    for (int i = 0; i != g.size(); ++i)
    {
        cout << g[(index + i) % g.size()].x << " " << g[(index + i) % g.size()].y << endl;
    }
    return 0;
}


Measured memory_bytes: 10548