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

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

struct pct {
    double x, y;
};

int n, i, poz;
pct v[120001], sol[120001], aux, mini{999999999, 999999999};

double CrossProduct(pct A, pct B, pct C) {
    return (B.x - A.x) * (C.y - A.y) - (B.y - A.y) * (C.x - A.x);
}

bool cmp(pct a, pct b) {
    if(CrossProduct(v[0], a, b) < 0) {
        return false;
    }
    return true;
}

int main() {
    fin >> n;
    for(i = 0; i < n; i++) {
        fin >> v[i].x >> v[i].y;
        if(v[i].x <= mini.x) {
            mini = v[i];
            poz = i;
        }
    }
    aux = v[0];
    v[0] = v[poz];
    v[poz] = aux;
    sort(v+1, v+n, cmp);
    sol[0] = v[0];
    sol[1] = v[1];
    int nr = 1;
    for(i = 2; i < n; i++) {
        while(CrossProduct(sol[nr-1], sol[nr], v[i]) < 0) {
            nr--;
        }
        nr++;
        sol[nr] = v[i];
    }
    fout << nr + 1 << '\n';
    for(i = 0; i <= nr; i++) {
        fout << fixed << setprecision(6) << sol[i].x << ' ' << sol[i].y << '\n';
    }
    fin.close();
    fout.close();
    return 0;
}