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

struct Point {
    double X, Y;
};

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 det(p1, p2, minPoint)<0;
}

int main() {
    ifstream cin ("infasuratoare.in");
    ofstream cout ("infasuratoare.out");
    int n;
    cin>>n;
    vector<Point> points(n);
    for (int i = 0; i < n; i++) {
        cin>>points[i].X>>points[i].Y;
    }

    int p = 0;
    for (int i = 0; i < points.size(); i++) {
        if (points[p].X > points[i].X || points[p].X == points[i].X && points[p].Y>points[i].Y) {
            p = i;
        }
    }
    swap(points[0], points[p]);

    minPoint = points[0];
    sort(points.begin()+1, points.end(), comparePoints);
    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.end()-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;
}