#include <iostream>
#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
#define eps 1e-12
#define  p pair<double, double>
#define x first
#define y second
#define MAX 120100
double cross_product(p a, p b, p c)
{
    return a.x * b.y + b.x * c.y + c.x * a.y - b.y * c.x - c.y * a.x - a.y * b.x;
}

p a[MAX];
int st[MAX], viz[MAX];

int main()
{
    int n, i, dr;
    fin >> n;
    for(i = 1 ; i <= n ; i++)
    {
        fin >> a[i].first >> a[i].second;
    }
    sort(a + 1, a + n + 1);
    dr = 0;
    st[++dr] = 1;
    st[++dr] = 2;
    viz[2] = 1;
    for(i = 3 ; i <= n ; i++)
    {
        while(dr >= 2 && cross_product(a[st[dr - 1]], a[st[dr]], a[i]) < eps)
        {
            viz[st[dr--]] = 0;
        }

        st[++dr] = i;
        viz[i] = 1;

    }
    for(i = n ; i >= 1 ; i--)
    {
        if(!viz[i])
        {
            while(dr >= 2 && cross_product(a[st[dr - 1]], a[st[dr]], a[i]) < eps)
            {
                viz[st[dr--]] = 0;
            }
            st[++dr] = i;
            viz[st[dr]] = 1;
        }
    }
    fout << dr - 1 << "\n";
    fout << fixed << setprecision(6);
    for(i = 1 ; i < dr ; i ++)
    {
        fout << a[st[i]].first << " " << a[st[i]].second << "\n";
    }
}