#include <fstream>
#include <vector>
#include <iomanip>
#include <algorithm>
using namespace std;

#define x first
#define y second
#define sz size
#define add push_back
#define L S.sz()-1
#define erase pop_back

typedef double ld;
typedef pair <ld, ld> punct;
typedef vector <punct> poligon;

poligon P, S;
int n;

ifstream fin ("infasuratoare.in");
ofstream fout ("infasuratoare.out");

inline ld cross(punct A, punct B, punct C) {
	return (B.x - A.x) * (C.y - A.y) - (C.x - A.x) * (B.y - A.y);
}

inline bool cmp (punct A, punct B) {
	return cross(P[0], A, B) < 0;
}

int main() {
	fin >> n;
	int pos = 0;
	for (int i = 0; i < n; ++i) {
		punct p;
		fin >> p.x >> p.y;
		P.add(p);
		if (P[pos] > P[i])
			pos = i;
	}
	swap (P[pos], P[0]);
	poligon :: iterator it = P.begin();
	it++;
	sort(it, P.end(), cmp);
	S.add (P[0]);
	S.add (P[1]);
	for (int i = 2; i < n; ++i) {
		while (S.sz() > 1 && cross (S[L-1], S[L], P[i]) > 0) {
			S.erase();
		}
		S.add (P[i]);
	}
	fout << fixed << S.sz() << "\n";
	for (int i = L; i >= 0; --i)
		fout << setprecision(9) << S[i].x << " " << S[i].y << "\n";
	fout.close();
	return 0;
}