#include <iostream>
#include <fstream>
#include <algorithm>
#include <cmath>
#include <iomanip>
#define nmax 120005
#define E 0.000000000001

using namespace std;

struct point {
    double x, y;
}P[nmax];

int n, nrPoints;
int st[nmax];
bool viz[nmax];

bool cmp(point a, point b) {
    if (a.y == b.y)
        return a.x < b.x;
    return a.y < b.y;
}

double det(point a, point b, point o) {
    return (a.x - o.x) * (b.y - o.y) - (a.y - o.y) * (b.x - o.x);
}

int main() {
    
    ifstream fin("infasuratoare.in");
    ofstream fout("infasuratoare.out");
    
    fin >> n;
    for (int i = 1; i <= n; i++)
        fin >> P[i].x >> P[i].y;
    
    sort(P+1, P+n+1, cmp);
    
    st[1] = 1;
    st[2] = 2;
    viz[1] = viz[2] = true;
    nrPoints = 2;
    
    for (int i = 1; i <= n; i++) {
        while (nrPoints > 1 && det(P[st[nrPoints-1]], P[st[nrPoints]], P[i]) < E)
            viz[st[nrPoints--]] = false;
        st[++nrPoints] = i;
        viz[i] = true;
    }
    
    for (int i = n; i > 0; i--) {
        if (viz[i])
            continue;
        while (nrPoints > 1 && det(P[st[nrPoints-1]], P[st[nrPoints]], P[i]) < E)
            nrPoints--;
        st[++nrPoints] = i;
    }
    
    fout << --nrPoints << "\n";
    fout << fixed;
    for (int i = 1; i <= nrPoints; i++)
        fout << setprecision(6) << P[st[i]].x << " " << P[st[i]].y << "\n";
     
    fin.close();
    fout.close();
    
    return 0;
}