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

#define x first
#define y second

using namespace std;

ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");

int n,vf,poz,st[120005];

typedef pair <double, double> Punct;
Punct a[120005];

double determinant(Punct A, Punct B, Punct C)
{
    return (B.x - A.x) * (C.y - A.y) - (B.y - A.y) * (C.x - A.x);
}

int comp(Punct A, Punct B)
{
    return (determinant(a[1], A, B) < 0);
}

int main()
{
    f >> n;
    for(int i = 1; i <= n; i++)
    {
        f >> a[i].x >> a[i].y;
        if(a[i] < a[poz]) poz = i;
    }
    swap(a[1], a[poz]);
    sort(a + 2, a + n + 1, comp);
    st[++vf] = 1;
    for(int i = 2; i <= n; i++)
    {
        while(vf > 1 && determinant(a[st[vf-1]], a[st[vf]], a[i]) > 0) vf--;
        st[++vf] = i;
    }
    g << vf << '\n';
    while(vf)
    {
        g << fixed << setprecision(6) << a[st[vf]].x << ' ' << a[st[vf]].y << '\n';
        vf--;
    }
    g.close();
    return 0;
}