namespace AtCoder;

#nullable enable

using System.Numerics;

static class Extensions
{
    public static T[] Repeat<T>(this int time, Func<T> F) => Enumerable.Range(0, time).Select(_ => F()).ToArray();
}

class AtCoder
{
    object? Solve()
    {
        var t = Int();
        var ans = new List<List<(int, int)>>();
        for (var i = 0; i < t; i++)
        {
            ans.Add(Solve2());
        }
        foreach (var l in ans)
        {
            Out(l.Count);
            foreach (var (x, y) in l) Out(x + " " + y);
        }
        return null;
    }

    List<(int, int)> Solve2()
    {
        var res = new List<(int, int)>();
        var n = Int();
        var l = Int();
        var d = 500;
        var z = l / d + 1;
        var g = new List<(int, int)>[d, d];
        for (var i = 0; i < d; i++) for (var j = 0; j < d; j++) g[i, j] = new();
        for (var i = 0; i < n; i++)
        {
            var x = Int();
            var y = Int();
            g[x / z, y / z].Add((x, y));
        }
        for (var i = 0; i < d; i++) for (var j = 0; j < d; j++)
        {
            var a = g[i, j];
            if (a.Count == 0) continue;
            a.Sort();
            foreach (var (x, y) in a) res.Add((x, y));
        }
        return res;
    }

    public static void Main() => new AtCoder().Run();
    public void Run()
    {
        var res = Solve();
        if (res != null)
        {
            if (res is bool yes) res = yes ? "Yes" : "No";
            sw.WriteLine(res);
        }
        sw.Flush();
    }

    string[] input = Array.Empty<string>();
    int iter = 0;
    readonly StreamWriter sw = new(Console.OpenStandardOutput()) { AutoFlush = false };

    #pragma warning disable IDE0051
    string String()
    {
        while (iter >= input.Length) (input, iter) = (Console.ReadLine()!.Split(' '), 0);
        return input[iter++];
    }
    T Input<T>() where T : IParsable<T> => T.Parse(String(), null);
    int Int() => Input<int>();
    void Out(object? x, string? separator = null)
    {
        separator ??= Environment.NewLine;
        if (x is System.Collections.IEnumerable obj and not string)
        {
            var firstLine = true;
            foreach (var item in obj)
            {
                if (!firstLine) sw.Write(separator);
                firstLine = false;
                sw.Write(item);
            }
        }
        else sw.Write(x);
        sw.WriteLine();
    }
    #pragma warning restore IDE0051
}