#include <cstdio>
#include <iostream>
#include <algorithm>
#include <fstream>
#include <iomanip>

using namespace std;

#define x first
#define y second

typedef pair<double, double> point;

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

const int MAX_N = 120005;

int n;
point v[MAX_N];

point stiva[MAX_N];
int cnt;

void read() {
    f >> n;
    for (int i = 1; i <= n; ++i)
        f >> v[i].x >> v[i].y;
}

double  unghi (point a,point b,point c)
{
    return (b.x-a.x)*(c.y-a.y)-(c.x-a.x)*(b.y-a.y);
}
bool cmp(point a,point b)
{
    return (unghi(v[1],a,b)<0);
}
void sorteaza() {
    int pos = 1;
    for (int i = 2; i <= n; ++i)
        if (v[i] < v[pos])
            pos = i;
    swap(v[1], v[pos]);
    sort(v + 2, v + n + 1, cmp);
}

void infasoara() {
    sorteaza();
    //for(int i=1;i<=n;i++) cout<<v[i].x<<" "<<v[i].y<<'\n';

    stiva[1] = v[1];
    stiva[2] = v[2];
    cnt = 2;
    for (int i = 3; i <= n; ++i) {
        while (cnt >= 2 && unghi(stiva[cnt - 1], stiva[cnt], v[i]) > 0)
            --cnt;
        stiva[++cnt] = v[i];
    }
}

void afiseaza() {
    g << fixed;
    g << cnt << "\n";
    for (int i = cnt; i >= 1; --i)
        g << setprecision(9) << stiva[i].x << " " << stiva[i].y << "\n";
}

int main() {
    read();
    infasoara();
    afiseaza();
}