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

ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
struct Punct
{
    long double x, y;
    bool operator<(Punct A) const
    {
        if (A.y == y) return x < A.x;
        return y < A.y;
    }
};
Punct a[120003];
int n, st[120003], top, viz[120003];
int sol[120003], k;

long double F(Punct A, Punct B, Punct C)
{
    long double a, b, c;
    a = B.y - A.y;
    b = A.x - B.x;
    c = A.x*(A.y - B.y) + A.y * (B.x - A.x);
    return a * C.x + b * C.y + c;
}

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

int main()
{
    int i;
    Citire();
    sort(a + 1, a + n + 1);
    top = 1;
    st[top] = 1;
    viz[1] = 1;
    for (i = 2; i <= n; i++)
    {
        /// scot din stiva elemente cat timp
        /// F(st[top-1], st[top], a[i]) > 0
        while (top > 1 && F(a[st[top-1]], a[st[top]], a[i]) > 0)
        {
            viz[st[top]] = 0;
            top--;
        }
        st[++top] = i;
        viz[i] = 1;
    }
    k = top;
    for (i = 1; i <= top; i++)
        sol[i] = st[i];

    viz[1] = 0;
    top = 1;
    st[1] = n;
    for (i = n - 1; i >= 1; i--)
        if (viz[i] == 0)
        {
            /// scot din stiva elemente cat timp
            /// F(st[top-1], st[top], a[i]) > 0
            while (top > 1 && F(a[st[top-1]], a[st[top]], a[i]) > 0)
            {
                viz[st[top]] = 0;
                top--;
            }
            st[++top] = i;
            viz[i] = 1;
        }
    for (i = 2; i <= top; i++)
        sol[++k] = st[i];
    fout << k-1 << "\n";
    for (i = 1; i < k; i++)
    {
        fout<<setprecision(12)<<fixed<<
        a[sol[i]].x << " " << a[sol[i]].y << "\n";
    }
    fout.close();
    return 0;
}