#include <fstream>
#include <vector>
#include <algorithm>
#include <iomanip>

using namespace std;

ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

const int NMAX = 1e5;

struct point
{
    long double x, y;

    bool operator < (const point other) const
    {
        if(x == other.x)
            return y < other.y;

        return x < other.x;
    }
};

int N;
point v[NMAX + 5];
vector <point> hull;

long double CrossProd(point O, point A, point B)
{
    return (A.y - O.y) * (B.x - O.x) - (B.y - O.y) * (A.x - O.x);
}

inline bool cmp(const point A, const point B)
{
    return CrossProd(v[1], A, B) < 0;
}

void ReadAndComputeHull()
{
    fin >> N;

    int x, y;
    for(int i = 1; i <= N; i++)
    {
        fin >> x >> y;
        v[i] = {x, 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);

    hull.push_back(v[1]);

    for(int i = 2; i <= N; i++)
    {
        while(hull.size() > 1 && CrossProd(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';
}

int main()
{
    ReadAndComputeHull();

    return 0;
}