#include <bits/stdc++.h>

using namespace std;
ifstream in("infasuratoare.in");
ofstream out("infasuratoare.out");
struct punct
{
    double x;
    double y;
    double p;
};
const int nx = 120002;
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();
        else return numeric_limits < double > :: min();
    }
    return y/x;
}
bool crit (const punct &a, const punct &b)
{
    return a.p<b.p;
}
double det (punct a, punct b, punct c)
{
    return (a.x*b.y + b.x*c.y + c.x*a.y) - (a.x*c.y + b.x*a.y + c.x*b.y);
}
vector < int > sol;
punct v[nx];
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[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(vector < int > :: iterator it = sol.begin(); it!=sol.end(); it++)
        out<<fixed<<v[*it].x<<' '<<fixed<<v[*it].y<<'\n';
    return 0;
}