#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
#define x first
#define y second
#define MAX 120010
#define eps 1e-12
typedef double d;
pair<d, d> a[MAX];
int st[MAX], viz[MAX], dr;

d cross_product(pair<d, d> o, pair<d, d> a, pair<d, d> b)
{
    a.x -= o.x;
    a.y -= o.y;
    b.x -= o.x;
    b.y -= o.y;
    return a.x * b.y - a.y * b.x;
}

int main()
{
    int n, i;
    fin >> n;
    for(i = 1 ; i <= n ; i++)
    {
        fin >> a[i].x >> a[i].y;
    }

    sort(a + 1, a + n + 1);
    st[1] = 1;
    st[2] = 2;
    dr = 2;
    viz[2] = 1;
    for(i = 1 ; i <= n ; i++)
    {
        if(viz[i])
            continue;
        while(dr >= 2 && cross_product(a[st[dr - 1]], a[st[dr]], a[i]) < eps)
        {
            viz[st[dr]] = 0;
            dr--;
        }
        st[++dr] = i;
        viz[i] = 1;
    }
    for(i = n ; i >= 1 ; i--)
    {
        if(viz[i])
            continue;
        while(dr >= 2 && cross_product(a[st[dr - 1]], a[st[dr]], a[i]) < eps)
        {
            viz[st[dr]] = 0;
            dr--;
        }
        st[++dr] = i;
        viz[i] = 1;
    }
    fout << dr - 1 << "\n";
    for(i = 2 ; i <= dr ; i ++)
    {
        fout << a[st[i]].x << " " << a[st[i]].y << "\n";
    }
}