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

ifstream f ("infasuratoare.in");
ofstream g ("infasuratoare.out");

const int NMAX = 120000;

struct punct {
    double x, y;
};

int N, nrp;
punct P[NMAX+1], S[NMAX+1];

double det (const punct &A, const punct &B, const punct &C) {
    return (A.x - B.x) * (B.y - C.y) - (A.y - B.y) * (B.x - C.x);
}

bool compd(const punct &A, const punct &B) {
    return det(P[1], A, B) > 0;
}

bool compx(const punct &A, const punct &B) {
    if (A.x == B.x) return A.y < B.y;
    return A.x < B.x;
}

void citire() {
    f >> N;
    int pmin = 1;
    for (int i=1; i<=N; i++) {
        f >> P[i].x >> P[i].y;
        if (compx(P[i], P[pmin]))
            pmin = i;
    }
    swap(P[1], P[pmin]);
}

void Graham() {
    sort(P+2, P+N+1, compd);
    S[1] = P[1];
    S[2] = P[2];
    nrp = 2;
    for (int i=3; i<=N; i++) {
        while(nrp >= 2 && det(S[nrp-1], S[nrp], P[i]) < 0)
            nrp--;
        S[++nrp] = P[i];
    }
}

void afisare() {
    g << nrp << '\n';
    g << fixed << setprecision(6);
    for(int i = 1; i<=nrp; i++)
        g << S[i].x << ' ' << S[i].y << '\n';
}

int main()
{
    citire();
    Graham();
    afisare();
    f.close();
    g.close();
    return 0;
}