using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var t = NN;
        var ans = new long[t];
        for (var u = 0; u < t; ++u)
        {
            var c = NList;
            var (n, l, k) = (c[0], c[1], c[2]);
            var x = NList;
            var ok = (l + 1) / 2;
            var ng = 0;
            while (ok - ng > 1)
            {
                var mid = (ok + ng) / 2;
                var ev = new List<(int pos, int kind)>();
                for (var i = 0; i < n; ++i)
                {
                    if (x[i] - mid < 0)
                    {
                        ev.Add((0, 1));
                        ev.Add((x[i] + mid, -1));
                        ev.Add((x[i] - mid + l, 1));
                        ev.Add((l, -1));
                    }
                    else if (x[i] + mid > l)
                    {
                        ev.Add((0, 1));
                        ev.Add((x[i] + mid - l, -1));
                        ev.Add((x[i] - mid, 1));
                        ev.Add((l, -1));
                    }
                    else
                    {
                        ev.Add((x[i] - mid, 1));
                        ev.Add((x[i] + mid, -1));
                    }
                }
                ev.Sort((l, r) =>
                {
                    var d = l.pos.CompareTo(r.pos);
                    if (d != 0) return d;
                    return r.kind.CompareTo(l.kind);
                });
                // WriteLine("mid = " + mid);
                // WriteLine(string.Join(" ", ev));
                var flg = true;
                var count = 0;
                for (var i = 0; i < ev.Count; ++i)
                {
                    count += ev[i].kind;
                    if (i + 1 == ev.Count || ev[i].pos != ev[i + 1].pos || (ev[i].kind == 1 && ev[i + 1].kind == -1))
                    {
                        if (ev[i].pos != l && count < k)
                        {
                            // WriteLine($"mid = {mid}, ev = {ev[i]}, {count} < {k}");
                            flg = false;
                            break;
                        }
                    }
                }
                if (flg) ok = mid;
                else ng = mid;
            }
            ans[u] = ok;
        }
        WriteLine(string.Join("\n", ans));
    }
}