#include<stdio.h>
#include<algorithm>
using namespace std;
#define Nmax 120005
#define Inf 1000000010
FILE*f=fopen("infasuratoare.in","r");
FILE*g=fopen("infasuratoare.out","w");

int i,N,st,S[Nmax];
double ymin,xmin;

struct pct{
	double x;
	double y;
	double xinit;
	double yinit;
}A[Nmax];
	

int cmp( pct a, pct b ){
	return a.x * b.y > a.y * b.x ;
}

int det(int a,int b,int c){
	double aux = A[a].x * ( A[b].y - A[c].y ) + A[b].x * ( A[c].y - A[a].y ) + A[c].x * ( A[a].y - A[b].y ) ;
	
	if ( aux >= 0 )
		return 1;
	return 0;
	
}

int main () {
	fscanf(f,"%d",&N);
	
	xmin = ymin = Inf;
	for ( i = 1 ; i <= N ; ++i ){
		fscanf(f,"%lf %lf",&A[i].x,&A[i].y);
		if ( A[i].y < ymin ){
			ymin = A[i].y;
			xmin = A[i].x;
		}
	}
	
	for ( i = 1 ; i <= N ; ++i ){
		A[i].xinit = A[i].x;
		A[i].yinit = A[i].y;
		A[i].y -= ymin;
		A[i].x -= xmin;
	}
	sort(A+1,A+N+1,cmp);
	
	S[++st] = 1; S[++st] = 2;
	for ( i = 3 ; i <= N ; ++i ){
		while ( !det( S[st-1],  S[st],i ) && st > 2 )
			--st;
		S[++st] = i;
	}
	
	fprintf(g,"%d\n",st);
	for ( i = 1 ; i <= st ; ++i ){
		fprintf(g,"%lf %lf\n",A[S[i]].xinit,A[S[i]].yinit);
		
	}
	
	
	fclose(f);
	fclose(g);
	
	return 0;
}