import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.PriorityQueue;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int t = Integer.parseInt(br.readLine());
		PrintWriter pw = new PrintWriter(System.out);
		for (int z = 0; z < t; z++) {
			String[] sa = br.readLine().split(" ");
			int n = Integer.parseInt(sa[0]);
			int l = Integer.parseInt(sa[1]);
			int d = Math.max(1, (int) (l / Math.max(1.0, Math.sqrt(n / 1.5))));
			PriorityQueue<Obj> que = new PriorityQueue<>((o1, o2) -> {
				if (o1.x2 != o2.x2) {
					return o1.x2 - o2.x2;
				}
				if (o1.x2 % 2 == 0) {
					return o1.y - o2.y;
				} else {
					return o2.y - o1.y;
				}
			});
			for (int i = 0; i < n; i++) {
				sa = br.readLine().split(" ");
				Obj o = new Obj();
				o.x = Integer.parseInt(sa[0]);
				o.y = Integer.parseInt(sa[1]);
				o.x2 = o.x / d;
				que.add(o);
			}

			pw.println(n);
			while (!que.isEmpty()) {
				Obj o = que.poll();
				pw.println(o.x + " " + o.y);
			}
		}
		pw.flush();
		br.close();
	}

	static class Obj {
		int x, x2, y;
	}
}