#include <bits/stdc++.h>

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

int st[120005], top, n;
bool viz[120005];

struct db{
    double x, y;
}a[120006];


inline int F(int x, int y, int k)
{
    return a[x].x * a[y].y + a[y].x * a[k].y + a[k].x * a[x].y
        - a[k].x * a[y].y - a[k].y * a[x].x - a[y].x * a[x].y;
}

void Infasor()
{
    st[1] = 1;
    st[2] = 2;
    viz[2] = 1;
    top = 2;
    for(int i = 3; i <= n; i++)
    {
        while(top && F(st[top - 1], st[top], i) < 0)
            viz[st[top--]] = 0;
        viz[i] = 1;
        st[++top] = i;
    }
    for(int i = n - 1; i >= 1; i--)
        if(!viz[i])
        {
            while(top && F(st[top - 1], st[top], i) < 0)
                viz[st[top--]] = 0;
            viz[i] = 1;
            st[++top] = i;
        }

    fout << top - 1 << "\n";

    for(int i = 1; i < top; i++)
        fout << fixed << setprecision(13) << a[st[i]].x << " " << a[st[i]].y << "\n";
}

inline bool Cmp(const db A, const db B)
{
    if(A.y == B.y)
        return A.x < B.x;
    return A.y < B.y;
}

void Citire()
{
    fin >> n;
    for(int i = 1; i <= n; i++)
        fin >> a[i].x >> a[i].y;
    sort(a + 1, a + n + 1, Cmp);
    Infasor();
}

int main()
{
    Citire();
    return 0;
}