#include<iostream>
#include<iomanip>
#include<cstdio>
#include<cmath>
#include<algorithm>
#include<vector>
#include<utility>
#include<assert.h>
#define EPS (1e-10)
#define equals(a, b) (fabs((a) - (b)) < EPS)

using namespace std;

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(a * x, a * y); }
    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 fabs(x - p.x) < EPS && fabs(y - p.y) < EPS; 
    }
};

struct Segment {
    Point p1, p2;
};

typedef Segment Line;

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

typedef Point Vector;
typedef vector<Point> Polygon;

double norm(Vector a) {
    return a.x * a.x + a.y * a.y;
}

double abs(Vector a) {
    return sqrt(norm(a));
}

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) / norm(base);
    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 abs(a - b);
}

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

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

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;

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);
}

bool intersect(Circle c, Line l) {
    return (getDistanceLP(l, c.c) - c.r) < EPS;
}

bool intersect(Circle c1, Circle c2) {
    return (getDistance(c1.c, c2.c) - c1.r - c2.r) < EPS;
}

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 = abs(cross(base, s1.p1 - s2.p1));
    double d2 = abs(cross(base, s1.p2 - s2.p1));
    double t = d1 / (d1 + d2);
    return s1.p1 + (s1.p2 - s1.p1) * t;
}

pair<Point, Point> getCrossPoints(Circle c, Line l) {
    assert(intersect(c, l));
    Vector pr = project(l, c.c);
    Vector e = (l.p2 - l.p1) / abs(l.p2 - l.p1);
    double base = sqrt(c.r * c.r - norm(pr - c.c));
    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 = abs(c1.c - c2.c);
    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 contain(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 ( abs(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, N;
    double x, y;
    Polygon P;
    cin >> n;
    for ( int i = 0; i < n; i++ ) {
        cin >> x >> y;
        P.push_back(Point(x, y));
    }
    P = andrewScan(P);
    N = P.size();
    cout << N << endl;
    
    int I = N - 1;
    for ( int i = 0; i < N; i++ ) {
        if ( P[I].y - P[i].y > EPS  ) {
            I = i;
            continue;
        }
        if ( abs(P[I].y - P[i].y) < EPS ) {
            if (P[i].x < P[I].x) {
                I = i;
            }
            continue;
        }
    }
    
    for ( int i = 0; i < N; i++ ) {
        cout << P[(I + i) % N].x << " " << P[(I + i) % N].y << endl;
    }
    
    return 0;
}


Measured memory_bytes: 10592