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

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

struct punct
{
    long double x, y;
    bool operator<(const punct B) const
    {
        if (y == B.y) return x < B.x;
        return y < B.y;
    }
} A[120003];
int n, viz[120003];
int st[120003], top;

int F(int i, int j, int k)
{
    long double a, b, c;
    a = A[i].y - A[j].y;
    b = A[j].x - A[i].x;
    c = A[i].x * A[j].y - A[j].x * A[i].y;
    if (a * A[k].x + b * A[k].y + c < 0) return -1;
    return 1;
}

int main()
{
    int i;
    fin >> n;
    for (i = 1; i <= n; i++)
        fin >> A[i].x >> A[i].y;
    sort(A + 1, A + n + 1);
    st[1] = 1;
    st[2] = 2;
    top = 2; viz[1] = viz[2] = 1;
    for (i = 3; i <= n; i++)
    {
        while (top > 1 && F(st[top - 1], st[top], i) < 0)
        {
            viz[st[top]] = 0;
            top--;
        }
        st[++top] = i;
        viz[i] = 1;
    }
    viz[1] = 0;
    for (i = n; i >= 1; i--)
        if (viz[i] == 0)
        {
            while (top > 1 && F(st[top - 1], st[top], i) < 0)
            {
                viz[st[top]] = 0;
                top--;
            }
            st[++top] = i;
            viz[i] = 1;
        }
    fout << (top - 1) << "\n";
    for (i = 1; i < top; i++)
        fout << setprecision(12) << fixed << A[st[i]].x << " " << A[st[i]].y << "\n";
    return 0;
}

//0, 1, 3-5, 7-18, 21, 22, 24-27, 29, 30, 34-36, 42, 44, 45, 47, 48, 51, 54, 56-58