#include <fstream>
#include <vector>
#include <iomanip>
#include <cmath>
#include <algorithm>
#include <iostream>
#define dmax 120000
#define inf 1000000006

using namespace std;

ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

struct point {

    double x,y;
    /*
    bool operator<(point a)
    {
    return polar() > polar(a);

    }*/
    };

vector <point> v(120000);
vector <point> hull;
point a,b;
int n;
double s;

//functions declaration

void read();
//reads the input file

double area(point x1, point x2, point x3);
// calculates the area of the triangle formed by the two points x1 & x2 with the origin O(0,0)

void first();
// replaces the first element form the vectorwith the first element from the left;

bool compare(point p1, point p2);
// compares the two polar angles

double polar(point p1);
// returnes the polar angle of the point p1

void write();


//END of declarations

int main() {

    read();

    first();

for(int i=0;i<n;i++)
    cout<<polar(v[i])<<'\n';
a=v[0];

// sort them by the polar angle
    sort(v.begin()+1, v.begin()+n, compare);

//browsing the vector and verifying the points



hull.push_back(a);
hull.push_back(v[1]);


    for(int i=2; i<n; i++) {
     //verific daca elem curent e in poligon sau nu, daca e il bag in coada

    if(area(a,hull[hull.size()-1],v[i])>0){

hull[hull.size()-1]=v[i];
    }

else
    if(area(a,hull[hull.size()-1],v[i])<0){

a=hull[hull.size()-1];
hull.push_back(v[i]);

    }

//daca nu e ok il strg pe ultimul si il pun pe asta nou

    }
//hull.push_back(v[n-1]);
write();
    return 0;
    }


void read() {

    fin>>n;

    for(int i=0; i<n; i++)
        fin>>v[i].x>>v[i].y;

    }


double area(point p1, point p2, point p3) {

    return (p1.x*p2.y+p1.y*p3.x+p2.x*p3.y-p2.x*p1.y-p1.x*p3.y-p3.x*p2.y)/2;

    }
bool compare(point p1, point p2) {
    //cout<<p2.x<<' '<<p2.y<<';'<<polar(p1)<<' '<<polar(p2)<<'\n';

    //if(polar(p1)!=polar(p2))
        return (polar(p1)>polar(p2));

    //else return (p1.y>p2.y);
    }

void first() {

    point d;

    d.x=inf;
    d.y=-inf;
    int poz=0;

    for(int i=0; i<n; i++) {
        if(v[i].x<d.x) {

            d=v[i];
            poz=i;
            }
        else if(v[i].x==d.x) if(v[i].y>d.y) {

                d=v[i];
                poz=i;
                }
        }

    v[poz]=v[0];
    v[0]=d;

    }

double polar(point x1) {
point p1;
p1.x=x1.x-a.x;
p1.y=x1.y-a.y;
    return p1.y/(sqrt(p1.y*p1.y+p1.x*p1.x));

    }


void write() {
fout<<hull.size()<<'\n';
    for(int i=0; i<hull.size(); i++)
        fout<<fixed<<setprecision(12)<<hull[i].x<<' '<<hull[i].y<<'\n';
   // cout<<"END SEQ"<<'\n';
    }