#include <fstream>
#include <algorithm>
#include <iomanip>

using namespace std;

ifstream in("infasuratoare.in");
ofstream out("infasuratoare.out");
int n;
pair<long double, long double> v[120005];
pair<long double, long double> s[120005];

long double det(const pair<long double, long double> &a, const pair<long double, long double> &b, const pair<long double, long double> &c)
{
    return (b.first - a.first)*(c.second - a.second) - (c.first - a.first)*(b.second - a.second);
}

bool cmp(const pair<long double, long double> &a, const pair<long double, long double> &b)
{
    return det(v[1], a, b) > 0;
}

int main()
{
    in>>n;

    for(int i = 1; i<=n; i++)
    {
        in>>v[i].first>>v[i].second;
    }

    int poz = 1;
    for(int i = 1; i<=n; i++)
    {
        if(v[i] < v[poz])
        {
            poz = i;
        }
    }

    swap(v[1], v[poz]);
    sort(v + 2, v + n + 1, cmp);

    /*for(int i = 1; i<=n; i++)
    {
        out<<v[i].first<<" "<<v[i].second<<'\n';
    }*/

    s[1] = v[1];
    s[2] = v[2];
    int head = 2;

    for(int i = 3; i<=n; i++)
    {
        while(head >= 2 && det(s[head - 1], s[head], v[i]) < 0)
        {
            head--;
        }

        head++;
        s[head] = v[i];
    }

    out<<head<<'\n';
    for(int i = head; i>=1; i--)
    {
        out<<setprecision(9)<<fixed<<s[i].first<<" "<<s[i].second<<'\n';
    }

    return 0;
}