#include <fstream>
#include <algorithm>
#include <vector>
using namespace std;
ifstream cin("infasuratoare.in");
ofstream cout("infasuratoare.out");
int n;
pair<double, double> v[120001], p0;
vector<int> ans;


int dist(pair<double, double>& x, pair<double, double>& y)
{
    return (x.first - y.first) * (x.first - y.first) + (x.second - y.second) * (x.second - y.second);
}
int orient(pair<double, double> &a, pair<double, double> &b, pair<double, double> &c)
{
    int l = a.first * (b.second - c.second) + b.first * (c.second - a.second) + c.first * (a.second - b.second);
    if (l > 0)
        return 1;
    else if (l < 0)
        return -1;
    else
        return 0;
}
bool csort(pair<double, double> a, pair<double, double> b)
{
    int r = orient(p0, a, b);
    if (r == 0)
        return dist(p0, a) < dist(p0, b);
    else return r < 0;
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin >> n;
    if (n < 3)
    {
        cout << "0";
        return 0;
    }
    for (int i = 1; i <= n; i++)
    {
        cin >> v[i].first >> v[i].second;
        if (p0.second > v[i].second || (p0.second == v[i].second && p0.first > v[i].first))
            p0 = v[i];
    }
    sort(v + 1, v + 1 + n,csort);
    
    int i = n;
    while (i >= 0 && orient(p0, v[i], v[n]) == 0) i--;
    reverse(v + i + 1, v + 1 + n);
    
    for (int i = 1; i <= n; i++)
    {
        while (ans.size() > 1 && orient(v[ans[ans.size() - 2]], v[ans.back()], v[i]) > 0)
            ans.pop_back();
        ans.push_back(i);
    }
    reverse(ans.begin(),ans.end());
    cout << ans.size() << '\n';
    int l = 0;
    for (int i = 0; i < ans.size(); i++)
    {
        if (v[ans[i]] == p0)
        {
            l = i;
            break;
        }
    }
    for (int i = l; i < ans.size(); i++)
        cout << v[ans[i]].first << ' ' << v[ans[i]].second << '\n';
    for (int i = 0; i < l; i++)
        cout << v[ans[i]].first << ' ' << v[ans[i]].second << '\n';

    
    return 0;
}