#include <bits/stdc++.h>
#define Point pair <double, double>
#define x first
#define y second
FILE *fin  = freopen("infasuratoare.in", "r", stdin);
FILE *fout = freopen("infasuratoare.out", "w", stdout);
using namespace std;

const int NMAX = 120005;
const double ZERO = 1e-12;

int N;
Point v[NMAX];
bitset <NMAX> vis;
int st[NMAX], head;

void read()
{
    scanf("%d", &N);
    for (int i = 1; i <= N; ++ i)
        scanf("%lf %lf\n", &v[i].x, &v[i].y);
}

double cross_product(Point O, Point A, Point B)
{
    return (A.x - O.x) * (B.y - O.y) - (B.x - O.x) * (A.y - O.y);
}

void convex_hull()
{
    sort(v + 1, v + N + 1);

    st[1] = 1;
    st[2] = 2;
    head = 2;
    vis.set(2);

    for (int i = 1, p = 1; i > 0; i += (p = (i == N ? -p : p)))
    {
        if (vis.test(i)) continue;
        while (head > 1 && cross_product(v[st[head - 1]], v[st[head]], v[i]) < ZERO)
            vis.reset(st[head --]);
        st[++ head] = i;
        vis.set(i);
    }
}

void write()
{
    printf("%d\n", head - 1);
    for (int i = 1; i < head; ++ i)
        printf("%.6lf %.6lf\n", v[st[i]].first, v[st[i]].second);
}
int main()
{
    read();
    convex_hull();
    write();
}