#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

struct Point { int x, y, num; } P[512], CH[512];

double cross(Point o, Point a, Point b)
{
	return (a.x - o.x) * (b.y - o.y) - (a.y - o.y) * (b.x - o.x);
}

bool compare(Point a, Point b)
{
	return (a.y < b.y) || (a.y == b.y && a.x < b.x);
}


int Andrew_monotone_chain(int pointnum)
{
	// 將所有點依照座標大小排序
	sort(P, P + pointnum, compare);

	int m = 0;  // m 為凸包頂點數目

	// 包下半部
	for (int i = 0; i < pointnum; ++i)
	{
		while (m >= 2 && cross(CH[m - 2], CH[m - 1], P[i]) <= 0) m--;
		CH[m++] = P[i];
	}

	// 包上半部，不用再包入方才包過的終點，但會再包一次起點
	for (int i = pointnum - 2, t = m + 1; i >= 0; --i)
	{
		while (m >= t && cross(CH[m - 2], CH[m - 1], P[i]) <= 0) m--;
		CH[m++] = P[i];
	}

	return m;
}

int main()
{
	int set, pointnum, convexhullnum, end;

	cin >> set;
	cout << set << endl;
	for (int i = 0; i < set; i++)
	{
		cin >> pointnum;
		for (int j = 0; j < pointnum; j++)
		{
			cin >> P[j].x;
			cin >> P[j].y;
			P[j].num = j;
		}

		if (i != set - 1)
		cin >> end;

		convexhullnum = Andrew_monotone_chain(pointnum);

		cout << convexhullnum << endl;
		for (int j = 0; j < convexhullnum; j++)
		{
			cout << CH[j].x << " ";
			cout << CH[j].y << endl;
		}

		if (i != set - 1)
		cout << "-1" << endl;
	}

	system("pause");
	return 0;
}