#include <iostream>
#include <fstream>
#include <vector>
#include <cmath>
#include <algorithm>
using namespace std;

struct Point {
    double X, Y, A;
};

Point minPoint;

double det(Point p1, Point p2, Point p3) {
    return p1.X*p2.Y+p2.X*p3.Y+p3.X*p1.Y-p1.X*p3.Y-p2.X*p1.Y-p3.X*p2.Y;
}

bool comparePoints(Point p1, Point p2) {
    return p1.A<p2.A || p1.A==p2.A && p1.Y>p2.Y;
    //return det(minPoint, p1, p2)>=0;
}

int main() {
    //read data
    ifstream cin("infasuratoare.in");
    int n;
    cin>>n;
    vector<Point> points(n);
    for (int i = 0; i < n; i++) {
        cin>>points[i].X>>points[i].Y;
    }
    //minPoint
    //Point minPoint;
    minPoint = points[0];
    for (int i = 0; i < points.size(); i++) {
        if (minPoint.X > points[i].X || minPoint.Y == points[i].Y && minPoint.Y > minPoint.Y) {
            minPoint = points[i];
        }
    }
    for (int i = 0; i < points.size(); i++) {
        double dx = points[i].X-minPoint.X;
        double dy = points[i].Y-minPoint.Y;
        points[i].A = dx/sqrt(dx*dx+dy*dy);
    }
    sort(points.begin(), points.end(), comparePoints);
    //compute convex hull
    vector<Point> hull;
    hull.push_back(points[0]);
    hull.push_back(points[1]);
    hull.push_back(points[2]);
    for (int i = 3; i < points.size(); i++) {
        while (hull.size() > 2 && det(hull[hull.size()-2], hull[hull.size()-1], points[i])<=0) {
            hull.erase(hull.begin()+hull.size()-1);
        }
        hull.push_back(points[i]);
    }
    cout<<hull.size()<<"\n";
    for (int i = 0; i < hull.size(); i++) {
        cout<<hull[i].X<<" "<<hull[i].Y<<"\n";
    }
    return 0;
}