#include <stdio.h>
#include <math.h>
#include <iostream>
#include <string>
#include <stdlib.h>
#include <assert.h>
#include <time.h>
#include <algorithm>
#include <vector>
#include <cstdio>
#include <cstring>
#include <fstream>
#include <queue>
#include <cstdlib>
#include <iomanip>
using namespace std;

	
#define NMAX 120001
#define EPS 1e-12


struct point 
{
	double x, y;
};

int st[NMAX];
bool viz[NMAX];

int compare(const void *a, const void *b)
{
	point* _a = (point*)a ;
	point* _b = (point*)b;
	if ( _a->x == _b->x )
		return _a->y - _b->y;
	else
		return _a->x - _b->x;
}

double convex (point A, point B, point C)
{
	return (B.x - A.x) * (C.y - A.y) - (C.x - A.x) * (B.y - A.y);
}

int main()
{
	int N;
	FILE *f = fopen ("infasuratoare.in", "r");
	FILE *g = fopen ("infasuratoare.out", "w");
	fscanf (f, "%d", &N);

	point v[NMAX];
	//v = new point[N];

	for (int i = 1; i <= N; i++)
	{
		fscanf(f, "%lf %lf", &v[i].x, &v[i].y);
	}

	qsort(v, N, sizeof(point), compare);
	
    st[1] = 1; st[2] = 2; u = 2;
    vis[2] = true;
 
    for (int i = 1, p = 1; i > 0; i += (p = (i == N ? -p : p)))
	{
        if (vis[i])
			continue;
      
		while (u >= 2 && cross_product(v[st[u-1]], v[st[u]], v[i]) < EPS)
            vis[st[head--]] = false;
        
		st[++head] = i;
        vis[i] = true;
    }

	fprintf (g, "%d\n", u-1);
	
	for (int i = 0 ; i < u; i++)
		fprintf (g, "%.6lf %.6lf\n", v[st[i]].x, v[st[i]].y);
	
	fclose(f); fclose(g);
	return 0;
}