#include <cstdio>
#include <algorithm>

using namespace std;
FILE *f,*g;

struct name
{
    double x,y;
}v[120002];
int sol[120002];
bool viz[120002];

bool how(name A, name B)
{
    if(A.x!=B.x)
        return (A.x<B.x);
    return (A.y<B.y);
}
double det(int a, int b, int c)
{
    double x1,y1,x2,y2,x3,y3;
    x1=v[a].x;
    y1=v[a].y;
    x2=v[b].x;
    y2=v[b].y;
    x3=v[c].x;
    y3=v[c].y;
    double de=x1*y2+x2*y3+x3*y1-x3*y2-x1*y3-x2*y1;
    return de;

}
int main()
{
    f=fopen("infasuratoare.in","r");
    g=fopen("infasuratoare.out","w");
    int n;
    fscanf(f,"%d",&n);
    for(int i=1;i<=n;++i)
        fscanf(f,"%lf %lf",&v[i].x,&v[i].y);
    sort(v+1,v+n+1,how);
    int ok=1;
    sol[1]=1;///jonglam cu indicii
    sol[2]=2,viz[2]=1;
    int poz=3,ss=2;
    while(!viz[1])
    {
        while(viz[poz])
        {
            if(poz==n)
                ok=-1;
            poz+=ok;
        }
        while(ss>=2 && det(sol[ss-1],sol[ss],poz)<0)
            viz[sol[ss]]=0,--ss;
        sol[++ss]=poz;
        viz[poz]=1;
    }
    fprintf(g,"%d\n",ss-1);
    for(int i=2;i<=ss;++i)
        fprintf(g,"%lf %lf\n",v[sol[i]].x,v[sol[i]].y);
    fclose(f);
    fclose(g);
    return 0;
}