#include <bits/stdc++.h>
#define nmax 120003
using namespace std;

struct Punct
{
    double x, y;
};

int st[nmax], top, v[nmax];
Punct a[nmax];
int n;

///retunrneaza mai mic ca 0 daca punctul a[p] este in semiplanul - al dreptei 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[j].x*a[i].y;
}

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;
}

void Hill()
{
    int i;
    sort(a+1, a+1+n, 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;
}