#include <bits/stdc++.h>

using namespace std;

const int NMAX = 120005;
int N;
pair <double, double> points[NMAX];
bitset <NMAX> seen;

double det(pair <double, double> x, pair <double, double> y, pair <double, double> z)
{
    double val = 0;
    val += x.first * y.second;
    val += y.first * z.second;
    val += z.first * x.second;
    val -= z.first * y.second;
    val -= x.first * z.second;
    val -= y.first * x.second;
    return val;
}

int main()
{
    ifstream fin("infasuratoare.in");
    ofstream fout("infasuratoare.out");
    fin >> N;
    for (int i = 1;i <= N;++i)
        fin >> points[i].first >> points[i].second;
    sort(points + 1, points + N + 1);
    vector <int> stk;
    stk.push_back(1);
    for (int i = 2;i <= N;++i)
    {
        while (stk.size() >= 2 && det(points[stk[stk.size() - 2]], points[stk.back()], points[i]) < 0)
        {
            seen[stk.back()] = 0;
            stk.pop_back();
        }
        seen[i] = 1;
        stk.push_back(i);
    }
    for (int i = N;i >= 1;--i)
    {
        if (seen[i] == 1)
            continue;
        while (stk.size() >= 2 && det(points[stk[stk.size() - 2]], points[stk.back()], points[i]) < 0)
        {
            seen[stk.back()] = 0;
            stk.pop_back();
        }
        seen[i] = 1;
        stk.push_back(i);
    }
    stk.pop_back();
    fout << stk.size() << "\n";
    fout << setprecision(12) << fixed;
    for (auto& x : stk)
        fout << points[x].first << " " << points[x].second << "\n";
    fin.close();
    fout.close();
    return 0;
}