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

using namespace std;

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

pair < double,double > v[120005];
bool seen[120005],ok;
int st[120005];
int x,n,i , poz,vf;

double det(pair < int,int >  a,pair < int,int >  b,pair < int,int >  c)
{
    return -b.second*c.first - c.second*a.first - a.second*b.first + a.first*b.second + b.first*c.second + c.first*a.second;
}

bool cmp(pair<int,int > a,pair < int,int > b)
{
    if((a.second - v[1].second) * (b.first - v[1].first) < (b.second - v[1].second) * (a.first - v[1].first))
        return true;
    return false;
}

int main()
{
    f >> n;
    poz = 1;
    for(i = 1; i <= n; i++)
    {
        f >> v[i].first >> v[i].second;
        if(v[poz].first > v[i].first || (v[poz].first == v[i].first && v[poz].second > v[i].second))
            poz = i;
    }
    swap(v[1],v[poz]);
    sort(v + 2,v + n + 1 ,cmp);
    st[1] = 1;
    st[2] = 2;
    vf = 2;
    i = 3;
    while(i <= n)
    {
        while(vf > 2 && det(v[st[vf - 1]],v[st[vf]] , v[i]) < 0)
            vf--;
        st[++vf] = i;
        i++;
    }
    i = 1;
    g << vf << '\n';
    g << fixed << setprecision(6) ;
    while(i <= vf)
        g  << v[st[i]].first << " " << v[st[i]].second  << '\n' ,i++;
    return 0;
}