#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;
#define ll long long
#define pb push_back
#define mp make_pair
#define pii pair<int,int>
#define pdd pair<double,double>
#define x first
#define y second
#define Nmax 120000

pdd v[Nmax];
int S[Nmax];

double cross_product(pdd p1, pdd p2, pdd p3)
{
	return (p2.x - p1.x) * (p3.y - p1.y) - (p3.x - p1.x) * (p2.y - p1.y);
}

bool CMP(pdd p1, pdd p2)
{
	return cross_product(v[0], p1, p2) < 0;
}


int main()
{
    ifstream fin("infasuratoare.in");
    ofstream fout("infasuratoare.out");
    
    int i, n, pMin, xDif = 0, yDif = 0, vf;
    
    fin >> n;
    for(pMin = 0, i = 0; i < n; ++i)
	{
		fin >> v[i].x >> v[i].y;
		if(v[i] < v[pMin]) pMin = i;
	}
	swap(v[0], v[pMin]);
	
	/*xDif = v[pMin].x;
	yDif = v[pMin].y;
	for(i = 0; i < n; ++i) v[i].x -= xDif, v[i].y -= yDif;*/
	
	sort(v + 1, v + n, CMP);
	
	vf = -1;
	for(i = 0; i < n; ++i)
	{
		while(vf >= 1 && cross_product(v[S[vf - 1]], v[S[vf]], v[i]) > 0) --vf;
		S[++vf] = i;
	}
	
	fout << vf + 1 << '\n';
	while(vf >= 0)
	{
		fout << v[S[vf]].x + xDif << ' ' << v[S[vf]].y + yDif << '\n';
		--vf;
	}
	
    return 0;
}