#include <bits/stdc++.h>
#define nmax 120003
using namespace std;
struct punct{double x,y;};
int st[nmax],top,v[nmax];
///v vect viz
punct a[nmax];
int n;

///ret <0 daca a[p] e in semiplanul -al dr det de a[i],a[j]
double F(int i,int j,int p)
{
    return a[p].x*(a[i].y-a[j].y)+a[p].y*(a[j].x-a[i].x)+a[i].x*a[j].y-a[i].y*a[j].x;
}
void Citire()
{
    int i;
    ifstream fin("infasuratoare.in");
    fin>>n;
    for(i=1;i<=n;i++)
        fin>>a[i].x>>a[i].y;
    fin.close();
}
inline bool Compara(punct A,punct B)
{
    if(A.y==B.y)return A.x<B.x;
    return A.y<B.y;
}
///alg lui Hill
void Hill()
{
    int i;
    sort(a+1,a+n+1,Compara);
    st[++top]=1;
    st[++top]=2;
    v[2]=1;
    for(i=3;i<=n;i++)
    {
        while(top>1 && F(st[top-1],st[top],i)<0)
        {
            v[st[top]]=0;
            top--;
        }
        st[++top]=i;
        v[i]=1;
    }
    for(i=n-1;i>=1;i--)
        if(v[i]==0)
    {
        while(F(st[top-1],st[top],i)<0)
        {
            v[st[top]]=0;
            top--;
        }
        st[++top]=i;
        v[i]=1;
    }
}
void Afisare()
{
    int i;
    ofstream fout("infasuratoare.out");
    fout<<(top-1)<<"\n";
    for(i=1;i<top;i++)
        fout<<setprecision(12)<<fixed<<a[st[i]].x<<" "<<a[st[i]].y<<"\n";
}

int main()
{
    Citire();
    Hill();
    Afisare();
    return 0;
}