#include <bits/stdc++.h>
using namespace std;

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

int N;

struct Point
{
    long double x, y;

    bool operator < (const Point &other) const
    {
        return x < other.x;
    }
};

Point v[125000];
bool taken[125000];

int st[125000], vf;

long double Slope(Point A, Point B, Point C)
{
    return (C.y - A.y) * (B.x - A.x) - (C.x - A.x) * (B.y - A.y);
}

void solve()
{
    st[1] = 1;
    st[2] = 2;
    vf = 2;

    int pas = 1, crt = 2;
    taken[2] = true;

    while(taken[1] == false)
    {
        while(taken[crt] == true)
        {
            if(crt == N)
                pas = -1;
            crt += pas;
        }

        while(vf >= 2 && Slope(v[crt], v[st[vf]], v[st[vf - 1]]) > 0)
            taken[st[vf]] = false, vf--;
        taken[crt] = true;
        st[++vf] = crt;
    }
}

int main()
{
    fin >> N;

    for(int i = 1; i <= N; i++)
    {
        long double x, y;

        fin >> x >> y;

        v[i] = {x, y};
    }

    sort(v + 1, v + N + 1);

    solve();

    fout << vf - 1 << '\n';

    for(int i = 2; i <= vf; i++)
        fout << fixed << setprecision(12) << v[st[i]].x << " " << fixed << setprecision(12) << v[st[i]].y << '\n';

    return 0;
}