#include <fstream>
#include <algorithm>
using namespace std;
#define eps 1e-12
#define nmax 120002
int n,i,h;
typedef struct punct
{
    double x,y;
};
punct p[nmax];
punct v[nmax];
int s[nmax],ok[nmax];
inline int cmp1(double a,double b)
{
    if(a+eps<b)
        return 1;
    if(b+eps<a)
        return -1;
    return 0;
}
bool cmp(const punct a,const punct b)
{
    int t;
    t=cmp1(a.x,b.x);
    if(t!=0)
        return t==0;
    return (cmp1(a.y,b.y)==1);
}
int semn(punct a,punct b,punct c)
{
    double A,B,C;
    A=a.y-b.y;
    B=b.x-a.x;
    C=a.x*b.y-b.x*a.y;
    return cmp1(A*c.x+B*c.y+C,0);
}
void rezolva()
{
    int k,q;
    sort(v+1,v+n+1,cmp);
    s[1]=1;
    s[2]=2;
    ok[2]=1;
    k=2;
    i=3;
    q=1;
    while(!ok[1])
    {
        while(ok[i])
        {
            if(i==n)
                q=-1;
            i+=q;
        }
        while(k>=2&&semn(v[s[k-1]],v[s[k]],v[i])==-1)
        {
            ok[s[k--]]=0;
        }
        s[++k]=i;
        ok[i]=1;
    }
    h=k-1;
}
int main()
{
    ifstream in("infasuratoare.in");
    ofstream out("infasuratoare.out");
    in>>n;
    for(i=1;i<=n;i++)
    {
        in>>v[i].x>>v[i].y;
    }
    rezolva();
    out<<h<<endl;
    out<<v[s[1]].x<<" "<<v[s[1]].y<<endl;
    for(i=h;i>=2;i--)
    {
        out<<v[s[i]].x<<" "<<v[s[i]].y<<endl;
    }
    return 0;
}