#include <bits/stdc++.h>

using namespace std;

ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
int n;
struct punct{
    double x, y;
}puncte[120005];

vector<punct>rez;
int ind=1;

vector<punct>s;

class cmp{
public:
    bool operator()(punct a, punct b)
    {
        if (a.x==b.x)
            return a.y<b.y;
        return a.x<b.x;
    }
};

double determinant(punct a, punct b, punct c)
{
    return (a.x-c.x)*(b.y-c.y)-(a.y-c.y)*(b.x-c.x);
}

void adaugare(punct p)
{
    while(determinant(s[ind-1],s[ind],p)<0)
    {
        s.pop_back();
        ind--;
        if (ind==0)
            break;
    }
    s.push_back(p);
    ++ind;
}

int main()
{
    f >> n;
    for (int i=1; i<=n; ++i)
    {
        f >> puncte[i].x >> puncte[i].y;
    }
    sort(puncte+1,puncte+n+1,cmp());
    s.push_back(puncte[1]);
    s.push_back(puncte[2]);
    for (int i=3; i<=n; ++i)
    {
        adaugare(puncte[i]);
    }
    s.push_back(puncte[n-1]);
    ind++;
    for (int i=n-2; i>0; --i)
    {
        adaugare(puncte[i]);
    }
    s.pop_back();
    g << s.size() << '\n';
    for (auto &v:s)
    {
        g<<setprecision(6) << fixed << v.x <<' '<<v.y << '\n';
    }
    return 0;
}