#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, vf;

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

inline int cmp(const point& p1, const point& p2)
{
    return cross_product(p[0],p1,p2) > 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 convex_hull()
{
    sort_points();
    st[0] = p[0];
    st[1] = p[1];
    vf = 2;
    for(int i=2; i<n; i++)
    {
        while(vf >= 2 && cross_product(st[vf-2],st[vf-1],p[i]) < 0)
            vf--;
        st[vf++] = p[i];
    }
}

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

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);
}

int main()
{
    Read();
    convex_hull();
    Write();
    return 0;
}