#include <bits/stdc++.h>
#define NMax 120007

using namespace std;

ifstream fin ("infasuratoare.in");
ofstream fout ("infasuratoare.out");

struct DB
{
    double x, y;
}a[NMax];

int n, st[NMax], v[NMax], top;

void Read ()
{
    fin >> n;

    for (int i = 1; i <= n; i++)
        fin >> a[i].x >> a[i].y;
}

inline bool CMP (const DB A, const DB B)
{
    if (A.y == B.y)
        return A.x < B.x;
    return A.y < B.y;
}

inline int F (int p, int q, int k)
{
    return a[q].x * (a[k].y - a[p].y) +
            a[p].x * (a[q].y - a[k].y) +
            a[k].x * (a[p].y - a[q].y);
}

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

    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 Output ()
{
    fout << top - 1 << "\n";

    for (int i = 1; i < top; i++)
        fout << fixed << setprecision(12) << a[st[i]].x << " " << a[st[i]].y << "\n";

}
int main()
{
    Read();
    Hill();
    Output();
    return 0;
}