#include <bits/stdc++.h>

using namespace std;

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

const int NMAX = 120000;

struct punct {
    double x, y;
};

int N, nrP;
punct P[NMAX+1], st[NMAX+1];

double det(const punct& A, const punct& B, const punct& C) {
    return (A.x - B.x) * (A.y - C.y) - (A.y - B.y) * (A.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 graham() {
    sort(P+2, P+N+1, compd);
    st[1] = P[1];
    st[2] = P[2];

    nrP = 2;

    for(int i = 3; i <= N; i++) {
        while(nrP >= 2 && det(st[nrP-1], st[nrP], P[i]) > 0)
            nrP--;
        st[++nrP] = P[i];
    }
}

void show() {
    out << nrP << '\n';
    out << fixed << setprecision(6);
    for(int i = nrP; i >= 1; i--)
        out << st[i].x << ' ' << st[i].y << '\n';
}

int main()
{
    in >> N;
    int pMin = 1;
    for(int i = 1; i <= N; i++) {
        in >> P[i].x >> P[i].y;
        if(compx(P[i], P[pMin]))
            pMin = i;
    }
    swap(P[1], P[pMin]);

    graham();

    show();
    return 0;
}