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

#define x first
#define y second

typedef pair<double, double> Point;

const int MAX_N = 120005;
const double EPS = 1e-12;

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

int n;
Point v[MAX_N];
bool vis[MAX_N];
int st[MAX_N], head;

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

double cross_product(Point O, Point A, Point B)
{
    return (A.x - O.x) * (B.y - O.y) - (B.x - O.x) * (A.y - O.y);
}
void write()
{
    g << head - 1 << "\n";
    g <<setprecision(6)<<fixed;
    for (int i = 1; i < head; ++i)
        g << v[st[i]].x << " " << v[st[i]].y << "\n";
}
void convex_hull() {
    sort(v + 1, v + n + 1);
    st[1] = 1; st[2] = 2; head = 2;
    vis[2] = 1;
    int i=1,p=1;
    while(i>0)
    {
        if (i==n) p=-p;
        i+=p;
        if (vis[i]) continue;
        while (head >= 2 && cross_product(v[st[head - 1]], v[st[head]], v[i]) < EPS)
            vis[st[head--]] = 0;
        st[++head] = i;
        vis[i] = 1;
    }

}
int main()
{
    read();
    convex_hull();
    write();
}