#include <fstream>
#include <vector>
#include <iomanip>
#include <algorithm>
 
using namespace std;
 
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
 
const int NMAX = 120000;
 
struct pct
{
    long double x, y;
 
    bool operator < (const pct other) const
    {
        if(y == other.y)
            return x < other.x;
 
        return y < other.y;
    }
};
 
int N;
pct v[NMAX + 5];
 
long double CrossProduct(pct A, pct B, pct C)
{
    return (C.y - A.y) * (B.x - A.x) - (B.y - A.y) *(C.x - A.x);
}
 
inline bool cmp(const pct A, const pct B)
{
    return CrossProduct(v[1], A, B) > 0;
}
 
int main()
{
    fin >> N;
 
    for(int i = 1; i <= N; i++)
        fin >> v[i].x >> v[i].y;
 
    for(int i = 2; i <= N; i++)
        if(v[i] < v[1])
            swap(v[1], v[i]);
 
    sort(v + 2, v + N + 1, cmp);
 
    vector <pct> hull;
    hull.push_back(v[1]);
 
    for(int i = 2; i <= N; i++)
    {
        while(hull.size() > 1 && CrossProduct(hull[hull.size() - 2], hull[hull.size() - 1], v[i]) < 0)
            hull.pop_back();
 
        hull.push_back(v[i]);
    }
 
    fout << hull.size() << '\n';
    for(auto it : hull)
        fout << fixed << setprecision(12) << it.x << ' ' << fixed << setprecision(12) << it.y << '\n';
 
    return 0;
}