#include <bits/stdc++.h>

using namespace std;
ifstream in("infasuratoare.in");
ofstream out("infasuratoare.out");
const int nx=120002;
struct punct
{
    double x, y;
};
punct v[nx];
vector < punct > sol;
double det (punct a, punct b, punct c)
{
    double rez= (double) a.x*b.y+c.x*a.y+b.x*c.y-b.y*c.x-a.x*c.y-a.y*b.x;
    return (double) rez;
}
bool comp (const punct a, const punct b)
{
    return det(v[1],a,b)>0;
}
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]);
    sort(v+2,v+n+1,comp);
    for(int i=1; i<=n; i++)
    {
        while(sol.size()>1 && det(v[i],*(sol.end()-1),*(sol.end()-2))>0) sol.pop_back();
        sol.push_back(v[i]);
    }
    out<<sol.size()<<'\n';
    for(vector < punct > :: iterator it=sol.begin(); it!=sol.end(); it++)
        out<<fixed<<setprecision(12)<<it->x<<' '<<fixed<<setprecision(12)<<it->y<<'\n';
    return 0;
}