#include <bits/stdc++.h>
#define ite vector < int > :: iterator

using namespace std;
ifstream in("infasuratoare.in");
ofstream out("infasuratoare.out");
const int nx=120002;
struct punct
{
    double x;
    double y;
    double p;
};
punct v[nx];
vector < int > sol;
double panta (punct a, punct b)
{
    double y=b.y-a.y;
    double x=b.x-a.x;
    if(x==0)
    {
        if(y>0) return numeric_limits < double > :: max();
        if(y<0) return numeric_limits < double > :: min();
    }
    return y/x;
}
double det (punct a, punct b, punct c)
{
    double rez =(a.x*b.y+b.x*c.y+c.x*a.y)-(a.x*c.y+b.x*a.y+c.x*b.y);
    return rez;
}
bool crit (punct a, punct b)
{
    return a.p<b.p;
}
int n,mn;
int main()
{
    in>>n;
    in>>v[1].x>>v[1].y;
    mn=1;
    for(int i=2; i<=n; i++)
    {
        in>>v[i].x>>v[i].y;
        if(v[i].x<v[mn].x)
            mn=i;
        else if(v[i].x==v[mn].x && v[i].y<v[mn].y)
            mn=i;
    }
    swap(v[1],v[mn]);
    v[n+1]=v[1];
    v[1].p=0;
    for(int i=2; i<=n; i++)
        v[i].p=panta(v[1],v[i]);
    sort(v+2,v+n+1,crit);
    for(int i=1; i<=n; i++)
    {
        while(sol.size()>1 && det(v[*(sol.end()-2)],v[i],v[*(sol.end()-1)])>=0)
            sol.pop_back();
        sol.push_back(i);
    }
    out<<sol.size()<<'\n';
    for(ite it=sol.begin(); it!=sol.end(); it++)
        out<<fixed<<v[*it].x<<' '<<fixed<<v[*it].y<<'\n';
    return 0;
}