/*
Andrew's monotone chain convex hull algorithm
O(NlogN)
*/

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

typedef long long ll;
typedef complex<ll> pt;

const int N=1e5+10;

int n;
vector<pt> t, hull;

ll cross (pt a, pt b, pt c)
{
    return imag(conj(b-a)*(c-a));
}

bool cmp (const pt &z, const pt &w)
{
    if (real(z)==real(w)) return imag(z)<imag(w);
    return real(z)<real(w);
}

void convexHull ()
{
    sort (t.begin(), t.end(), cmp);

    for (int i=0; i<2; i++)
    {
        int initSize=hull.size();
        for (auto xt: t)
        {
            while (hull.size()>=initSize+2 && cross(hull[hull.size()-2], hull[hull.size()-1], xt)<=0) hull.pop_back();
            hull.push_back(xt);
        }

        hull.pop_back();
        reverse(t.begin(), t.end());
    }
}

int main()
{
    scanf ("%d", &n);
    t.resize(n);
    for (int i=0;i<n;i++)
    {
        ll a, b;
        scanf ("%lld%lld", &a, &b);
        t[i]=pt(a, b);
    }

    convexHull();

    printf ("%d\n", hull.size());
    for (auto xt: hull) printf ("%lld %lld\n", real(xt), imag(xt));

    return 0;
}