#include <iostream>
#include <fstream>
#include <algorithm>
#include <iomanip>

using namespace std;

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

const int MAXN = 120010;

struct point
{
    double x, y;
} V[MAXN], St[MAXN];

inline double cp (const point &A, const point &B, const point &C)
{
    return (double) (B.x - A.x) * (C.y - A.y) - (B.y - A.y) * (C.x - A.x);
}

struct comp
{
    const point def;

    comp (const point &x):
        def (x)
        {}

    const inline bool operator () (const point &A, const point &B)
    {
        return cp (def, A, B) < 0;
    }
};

int main()
{
    int N, i, lv, ind;

    in >> N;
    for (i = 1; i <= N; i ++)
        in >> V[i].x >> V[i].y;

    ind = 1;
    for (i = 2; i <= N; i ++)
        if (V[i].x < V[ind].x || (V[i].x == V[ind].x && V[i].y < V[ind].y))
            ind = i;

    swap (V[1], V[ind]);
    sort (V + 2, V + N + 1, comp (V[1]));
    St[1] = V[1];
    St[2] = V[2];
    lv = 2;

    for (i = 3; i <= N; i ++){
        while (lv >= 2 && cp (St[lv - 1], St[lv], V[i]) > 0)
            lv --;

        St[++ lv] = V[i];
    }

    out << lv << "\n";

    out << fixed << setprecision (6);
    for (i = lv; i; i --)
        out << St[i].x << " " << St[i].y << "\n";

    return 0;
}