#include <iostream>
#include <fstream>
#include <algorithm>
#include <iomanip>
#define Nmax 120005

using namespace std;

ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");

const double EPS=1e-12;
struct point{
double x, y;
}a[Nmax];
double x, y;
int n, st[Nmax];
bool seen[Nmax];

bool cmp(point a, point b)
{
    if(a.x == b.x) return a.y < b.y;
    return a.x < b.x;
}

void print()
{
    for (int i = 1; i <= n; i++)
        cout << fixed << setprecision(2) << double(a[i].x) << " " << fixed << setprecision(2) << double(a[i].y) << '\n';
        cout << '\n';
}

double determinant(point a, point b, point c)
{
    return a.x*b.y + b.x*c.y + a.y*c.x - b.y*c.x - c.y*a.x - b.x*a.y;
}

int main()
{
    f >> n;
    for (int i = 1; i <= n; i++)
    {
        f >> x >> y;
        a[i]={x, y};
    }
    sort(a+1, a+n+1, cmp);
    //print();
    st[1]=1, st[2]=2;
    seen[2]=1;
    int i=2, top=2;
    for (int i = 3; i <= n; i++)
    {
        if(seen[i] == 1) continue;
        while(top>=2 && determinant(a[st[top]], a[st[top-1]], a[i])<EPS)
        {
            seen[st[top]]=0;
            top--;
        }
        st[++top]=i;
        seen[i]=1;
    }
    for (int i = n-1; i >= 1; i--)
    {
        if(seen[i] == 1) continue;
        while(top>=2 && determinant(a[st[top]], a[st[top-1]], a[i])<EPS)
        {
            seen[st[top]]=0;
            top--;
        }
        st[++top]=i;
        seen[i]=1;
    }
    g << top-1<< '\n';
    for (int i = top-1; i > 0; i--) g << fixed << setprecision(6) << a[st[i]].x << " " << fixed << setprecision(6) << a[st[i]].y << '\n';

    return 0;
}