#include <bits/stdc++.h>
using namespace std;
int n;
char c;
struct Point
{
    double x, y;
} points[100005], convexHull[100005];
double crossProduct(Point a1, Point a2, Point b1, Point b2)
{
    return (a2.x - a1.x) * (b2.y - b1.y) - (b2.x - b1.x) * (a2.y - a1.y);
}
double distance(Point p1, Point p2)
{
    return sqrt((p2.y - p1.y) * (p2.y - p1.y) + (p2.x - p1.x) * (p2.x - p1.x));
}
bool compare(Point p1, Point p2)
{
    double tmp = crossProduct(points[1], p1, points[1], p2);
    if (tmp > 0)
        return true;
    if (tmp == 0 && distance(points[0], p1) < distance(points[0], p2))
        return true;
    return false;
}
void solve()
{
    scanf("%d", &n);
    for (int i = 1; i <= n; i++)
    {
        scanf("%lf %lf %c", &points[i].x, &points[i].y, &c);
        if (i != 1 && points[i].y < points[1].y)
        {
            swap(points[1], points[i]);
        }
    }
    sort(points + 2, points + 1 + n, compare);
    convexHull[1] = points[1];
    int cnt = 1;
    for (int i = 2; i <= n; i++)
    {
        while (cnt > 1 && crossProduct(convexHull[cnt - 1], convexHull[cnt], convexHull[cnt], points[i]) < 0)
        {
            cnt--;
        }
        cnt++;
        convexHull[cnt] = points[i];
    }
    double perimeter = 0;
    int ans = 1;
    for (int i = 2; i <= cnt; i++)
    {
        if (convexHull[i].x < convexHull[ans].x)
            ans = i;
        if (convexHull[i].x == convexHull[ans].x && convexHull[i].y < convexHull[ans].y)
            ans = i;
    }
    cout << cnt << '\n';
    for (int i = ans; i <= cnt; i++)
        cout << convexHull[i].x << ' ' << convexHull[i].y << '\n';
    for (int i = 1; i < ans; i++)
        cout << convexHull[i].x << ' ' << convexHull[i].y << '\n';
    return;
}

int main()
{
    int t;
    cin >> t;
    while (t--)
        solve();
}

验证码 mmmp 祭