#include <fstream>
#include <vector>
#include <algorithm>
#include <cstdio>
#include <iomanip>
 
#define INF 1000000002
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
 
struct Point{double x, y;};
int n;
Point p[120002];
vector<Point> co;
 
double sign(Point p1, Point p2, Point p3)
{
    return (p1.x * p2.y + p1.y * p3.x + p2.x * p3.y) - (p2.y * p3.x + p2.x * p1.y + p1.x * p3.y);
}
 
bool test(Point p1, Point p2)
{
    return sign(p[0], p1, p2) < 0;
}
 
int main()
{
    fin >> n;
 
    int maxX = -INF;
    int pos = 0;
    for(int i = 0; i < n; i ++)
    {
        fin >> p[i].x >> p[i].y;
        if(p[i].x < p[pos].x || (p[i].x == p[pos].x && p[i].y < p[pos].y))
            pos = i;
    }
 
    swap(p[0], p[pos]);
    sort(p + 1, p + n, test);
 
    co.push_back(p[0]);
    for(int i = 1; i < n; i++)
    {
        while(co.size() > 1 && sign(co[co.size() - 2], co[co.size() - 1], p[i]) > 0)
            co.pop_back();
        co.push_back(p[i]);
    }
 
    fout << co.size() << '\n';
    fout << fixed << setprecision(6);
    for(int i = co.size() - 1; i >= 0; i --)
        fout << co[i].x << ' ' << co[i].y << '\n';
    return 0;
}