#include<cstdio>
#include<algorithm>
#define N_MAX 120000
using namespace std;

struct point
{
    double x, y;
};

point p[N_MAX], st[N_MAX];
int n, head;

void Read()
{
    FILE *fin = fopen("infasuratoare.in","r");
    fscanf(fin,"%d",&n);
    for(int i=0; i<n; i++)
        fscanf(fin,"%lf%lf",&p[i].x,&p[i].y);
    fclose(fin);
}

inline double det(point a, point b, point c)
{
    return (b.x-a.x)*(c.y-a.y) - (b.y-a.y)*(c.x-a.x);
}

inline int cmp(point a, point b)
{
    return det(p[0],a,b) > 0;
}

void sort_points()
{
    int i, minIndex = 0;
    for(i=1; i<n; i++)
        if(p[i].y < p[minIndex].y)
            minIndex = i;
        else if(p[i].y == p[minIndex].y && p[i].x < p[minIndex].x)
            minIndex = i;
    swap(p[0],p[minIndex]);
    sort(p+1,p+n,cmp);
}

void ConvexHull()
{
    st[0] = p[0];
    st[1] = p[1];
    head = 2;
    for(int i=2; i<n; i++)
    {
        while(head >= 2 && det(st[head-2],st[head-1],p[i]) < 0)
            head--;
        st[head++] = p[i];
    }
}

void Write()
{
    FILE *fout = fopen("infasuratoare.out","w");
    fprintf(fout,"%d\n",head);
    for(int i=0; i<head; i++)
        fprintf(fout,"%.6f %.6f\n",st[i].x,st[i].y);
    fclose(fout);
}

int main()
{
    Read();
    sort_points();
    ConvexHull();
    Write();
    return 0;
}