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

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

const double EPS = 1e-12;
struct Point
{
    long double x, y;
    bool operator<(Point A) const
    {
        if (A.y == y) return x < A.x;
        return y < A.y;
    }
};
Point a[120003];
int n, st[120003], top, viz[120003];
int sol[120003], k;

double cp(Point O, Point A, Point B) {
    return (A.x - O.x) * (B.y - O.y) - (B.x - O.x) * (A.y - O.y);
}

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

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

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

int main()
{
    int i;
    fin >> n;
    for (int i = 1; i <= n; i++)
        fin >> a[i].x >> a[i].y;
    convex_hull();
    return 0;
}