#include <fstream>
#include <iomanip>
#include <algorithm>
#define x first
#define y second
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
int n,mipoz;
typedef pair <double, double> Punct;
Punct p[120010];
 int st[10000000];
 int vf;
double determinant(Punct A, Punct B, Punct C)
{
    return (B.x - A.x) * (C.y - A.y) - (B.y - A.y) * (C.x - A.x);
}
 
int comp(Punct A, Punct B)
{if(determinant(p[1], A, B) < 0)
		return true;
return false;
	
 }
 
 void read()
 { fin >> n;
    for(int i = 1; i <= n; i++)
    {
        fin >> p[i].x >> p[i].y;
        if(p[i] < p[mipoz]) mipoz = i;
    }
 }
 
int main()
{
    
    swap(p[1], p[mipoz]);
    sort(p+ 2, p + n + 1, comp);
    st[++vf] = 1;
    for(int i = 2; i <= n; i++)
    {
        while(vf > 1 && determinant(p[st[vf-1]], p[st[vf]], p[i]) > 0) 
				vf--;
        st[++vf] = i;
    }
    fout << vf << '\n';
    while(vf)
    {
        fout <<setprecision(6)  << fixed << p[st[vf]].x << ' ' << p[st[vf]].y << '\n';
        vf--;
    }
    return 0;
    }