#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <iomanip>
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 p1.X < p2.X || p1.X==p2.X && p1.Y < p2.Y;
}

bool compareAngles(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 = min_element(points.begin(), points.end(), comparePoints) - points.begin();
    swap(points[0], points[p]);
    minPoint = points[0];

    sort(points.begin()+1, points.end(), compareAngles);

    vector<Point> hull;
    hull.push_back(points[0]);
    hull.push_back(points[1]);
    for (int i = 2; i < points.size(); i++) {
        while (hull.size()>1 && 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<<setprecision(9)<<hull[i].X<<" "<<hull[i].Y<<"\n";
    }
    return 0;
}