#include <fstream>
#include <iomanip>
#include <vector>
#include <algorithm>

struct COORD{ long double x,y; };


inline long double mycrossproduct(const COORD &p1, const COORD &p2, const COORD &p3){
	return (p2.x-p1.x)*(p3.y-p1.y)-(p2.y-p1.y)*(p3.x-p1.x);
}

COORD primul_punct;
inline bool comp_unghi(const COORD &a, const COORD &b){
	return mycrossproduct(primul_punct,a,b)<0;
}

int main(){
	std::ifstream fin("infasuratoare.in");
	std::ofstream fout("infasuratoare.out");

	unsigned n; fin>>n;

	std::vector<COORD> puncte(n);
	for(unsigned i=0;i<n;++i) fin>>puncte[i].x>>puncte[i].y;

	unsigned pos=0;
	for(unsigned i=1;i<n;++i)
		if(puncte[i].x<puncte[pos].x || ((puncte[i].x==puncte[pos].x)&&(puncte[i].y<puncte[pos].y)))
			pos=i;

	primul_punct=puncte[pos];
	COORD temp=puncte[0]; puncte[0]=primul_punct; puncte[pos]=temp;
	std::sort(puncte.begin()+1,puncte.end(),comp_unghi);

	std::vector<COORD> st(n);
	st[0]=puncte[0]; st[1]=puncte[1];
	unsigned top=1;

	for(unsigned i=2;i<n;++i){
		while(top>0 && mycrossproduct(st[top-1],st[top],puncte[i])>0) --top;
		st[++top]=puncte[i];
	}

	fout<<(top+1)<<"\n";
	fout<<std::fixed<<std::setprecision(6);
	for(int i=top;i>=0;--i) fout<<st[i].x<<" "<<st[i].y<<"\n";

	fout.close();
}