#include <bits/stdc++.h>

using namespace std;
struct date
{
    double x, y;
} v[120005];
vector<date>jos,sus;
double eps=1e-12;
bool cmp(date a, date b)
{
    if(a.x-b.x<eps)
        return a.y<b.y;
    return a.x<b.x;
}
int main()
{
    ifstream cin("infasuratoare.in");
    ofstream cout("infasuratoare.out");
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    int n;
    cin>>n;
    for(int i=1; i<=n; i++)
        cin>>v[i].x>>v[i].y;
    sort(v+1, v+n+1, cmp);
    jos.push_back(v[1]);
    jos.push_back(v[2]);
    for(int i=3; i<=n; i++)
    {
        while(jos.size()>=2 && atan2(jos[jos.size()-2].y-jos[jos.size()-1].y, jos[jos.size()-2].x-jos[jos.size()-1].x)>atan2(jos[jos.size()-2].y-v[i].y, jos[jos.size()-2].x-v[i].x))
            jos.pop_back();
        jos.push_back(v[i]);
    }
    sus.push_back(v[n]);
    sus.push_back(v[n-1]);
    for(int i=n-2; i>=1; i--)
    {
        while(sus.size()>=2 && atan2(sus[sus.size()-2].y-sus[sus.size()-1].y, sus[sus.size()-2].x-sus[sus.size()-1].x)>atan2(sus[sus.size()-2].y-v[i].y, sus[sus.size()-2].x-v[i].x))
            sus.pop_back();
        sus.push_back(v[i]);
    }
    cout<<jos.size()+sus.size()-2<<'\n';
    for(int i=0; i<jos.size()-1; i++)
        cout<<setprecision(6)<<fixed<<jos[i].x<<" "<<jos[i].y<<'\n';
    for(int i=0; i<sus.size()-1; i++)
        cout<<setprecision(6)<<fixed<<sus[i].x<<" "<<sus[i].y<<'\n';
    return 0;
}