#include <cstdio>
#include <cmath>
#include <algorithm>
using namespace std;
const double eps=1.e-12;
struct point
{
    double x,y;
};
point p[120050];
int st[120005];
int ccw(point a,point b,point c)
{
    double cp;
    cp=(b.x-a.x)*(c.y-b.y)-(b.y-a.y)*(c.x-b.x);
    if (fabs(cp)<eps)
        return 0;
    if (cp>=eps)
        return 1;
    return -1;
}
bool cmp(point a,point b)
{
    if (ccw(p[0],a,b)==-1)
        return 0;
    return 1;
}
int main()
{
    freopen("infasuratoare.in","r",stdin);
    freopen("infasuratoare.out","w",stdout);
    int n,i,top;
    double tx,ty;
    scanf("%d%lf%lf",&n,&tx,&ty);
    p[0].x=tx;p[0].y=ty;
    for (i=1;i<n;++i)
    {
        scanf("%lf%lf",&tx,&ty);
        p[i].x=tx;
        p[i].y=ty;
        if ((fabs(ty-p[0].y)<eps&&tx-p[0].x<=-eps)||(ty-p[0].y<=-eps))
            swap(p[0],p[i]);
    }
    sort (p+1,p+n,cmp);
    p[n]=p[0];
    st[0]=0;st[1]=1;top=1;i=2;
    while (i<=n)
    {
        if (ccw(p[st[top-1]],p[st[top]],p[i])==1)
        {
            st[++top]=i;
            ++i;
        }
        else
            --top;
    }
    printf("%d\n",top);
    for (register int j=0;j<top;++j)
        printf("%lf %lf\n",p[st[j]].x,p[st[j]].y);
    return 0;
}