Problem:
Score : 400 points

Problem Statement

Joisino is planning to record N TV programs with recorders.

The TV can receive C channels numbered 1 through C.

The i-th program that she wants to record will be broadcast from time s_i to time t_i (including time s_i but not t_i) on Channel c_i.

Here, there will never be more than one program that are broadcast on the same channel at the same time.

When the recorder is recording a channel from time S to time T (including time S but not T), it cannot record other channels from time S-0.5 to time T (including time S-0.5 but not T).

Find the minimum number of recorders required to record the channels so that all the N programs are completely recorded.

Constraints

1≤N≤10^5

1≤C≤30

1≤s_i<t_i≤10^5

1≤c_i≤C

If c_i=c_j and i≠j, either t_i≤s_j or s_i≥t_j.

All input values are integers.

Input

Input is given from Standard Input in the following format:

N C
s_1 t_1 c_1
:
s_N t_N c_N

Output

When the minimum required number of recorders is x, print the value of x.

Sample Input 1

3 2
1 7 2
7 8 1
8 12 1

Sample Output 1

2

Two recorders can record all the programs, for example, as follows:

With the first recorder, record Channel 2 from time 1 to time 7. The first program will be recorded. Note that this recorder will be unable to record other channels from time 0.5 to time 7.

With the second recorder, record Channel 1 from time 7 to time 12. The second and third programs will be recorded. Note that this recorder will be unable to record other channels from time 6.5 to time 12.

Sample Input 2

3 4
1 3 2
3 4 4
1 4 3

Sample Output 2

3

There may be a channel where there is no program to record.

Sample Input 3

9 4
56 60 4
33 37 2
89 90 3
32 43 1
67 68 3
49 51 3
31 32 3
70 71 1
11 12 3

Sample Output 3

2

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using static System.Console;
using static System.Math;
using static CS_Contest.Utils;
using System.Numerics;
using System.Linq.Expressions;
using Nakov.IO;
using static Nakov.IO.Cin;

//using static CS_Contest.Library;

namespace CS_Contest {
	using Li = List<int>;
	using LLi = List<List<int>>;
	using Ll = List<long>;

	internal class Program {
		private static void Main(string[] args) {
			var sw = new StreamWriter(OpenStandardOutput()) { AutoFlush = false };
			SetOut(sw);
			new Calc().Solve();
			Out.Flush();
		}

		public class Calc {
			public void Solve() {
				int N = NextInt(), C = NextInt();
				var list = new List<Tuple<int, int>>();
				REP(N, _ =>
				{
					list.Add(new Tuple<int, int>(NextInt(),NextInt()));
					NextInt();
				});
				list = list.OrderBy(_ => _.Item1).ToList();

				var rec = new Li();
				rec.Add(0);

				foreach (var tuple in list) {
					bool flag = false;
					for (int i = 0; i < rec.Count; i++) {
						if (rec[i] < tuple.Item1) {
							rec[i] = tuple.Item2;
							flag = true;
							break;
						}
					}
					if (flag) continue;
					rec.Add(tuple.Item2);
				}
				rec.Count.WL();


				return;
			}


		}
	}

	public static class Utils {
		public static long ModValue = (long)1e9 + 7;
		public static long INF = long.MaxValue;

		public static long Mod(long x) => x % ModValue;

		public static long ModPow(long x, long n) {
			long tmp = 1; while (n != 0) { if (n % 2 == 1) { tmp = Mod(tmp * x); } x = Mod(x * x); n /= 2; }
			return tmp;
		}

		public static long DivMod(long x, long y) => Mod(x * ModPow(y, (long)(1e9 + 5)));

		public static void WL(this object obj) => WriteLine(obj);

		public static void WL(this string obj) => WriteLine(obj);

		public static void WL<T>(this IEnumerable<T> list) => list.ToList().ForEach(x => x.WL());

		public static Li ReadInts() => ReadLine().Split().Select(int.Parse).ToList();

		public static string StringJoin<T>(this IEnumerable<T> l, string separator = "") => string.Join(separator, l);

		public static long GCD(long m, long n) {
			long tmp;
			if (m < n) { tmp = n; n = m; m = tmp; }
			while (m % n != 0) {
				tmp = n;
				n = m % n;
				m = tmp;
			}
			return n;
		}

		public static long LCM(long m, long n) => m * (n / GCD(m, n));

		public static void REP(int n, Action<int> act) {
			for (var i = 0; i < n; i++) {
				act(i);
			}
		}


		public static int ManhattanDistance(int x1, int y1, int x2, int y2) => Abs(x2 - x1) + Abs(y2 - y1);

		public struct IndexT<T> {
			public T Value { get; set; }
			public int Index { get; set; }

			public IndexT(T v, int i) {
				Value = v; Index = i;
			}
			public override string ToString() {
				return Value + " " + Index;
			}
		}

		public static IEnumerable<IndexT<T>> ToIndexEnumerable<T>(this IEnumerable<T> list) => list.Select((x, i) => new IndexT<T>(x, i));

		public static Queue<T> ToQueue<T>(this IEnumerable<T> iEnumerable) {
			var rt = new Queue<T>();
			foreach (var item in iEnumerable) {
				rt.Enqueue(item);
			}
			return rt;
		}

		public static IndexT<T> IndexOf<T>(this IEnumerable<T> ie, Func<IndexT<T>, IndexT<T>, IndexT<T>> func) =>
			ie.ToIndexEnumerable().Aggregate(func);


		public static T[] Range<T>(int range,Func<int,T> func) {
			var rt = new T[range];
			for (var i = 0; i < range; i++) rt[i] = func(i);
			return rt;
		}
		public static void Swap<T>(ref T x,ref T y) {
			var tmp = x;
			x = y;
			y = tmp;
		}


		public static Dictionary<TKey,int> CountUp<TKey>(this IEnumerable<TKey> l) {
			var dic = new Dictionary<TKey, int>();
			foreach (var item in l) {
				if (dic.ContainsKey(item)) dic[item]++;
				else dic.Add(item, 1);
			}
			return dic;
		}


		public static int Count<T>(this IEnumerable<T> l, T target) => l.Count(x => x.Equals(target));

		public static int UpperBound<T>(this IEnumerable<T> list,T target) where T : IComparable {
			var idx=list.ToList().BinarySearch(target);
			idx = idx < 0 ? ~idx : (idx+1);
			return Min(idx, list.Count());
		}

		public static int LowerBound<T>(this IEnumerable<T> list, T target) where T : IComparable {
			var idx = list.ToList().BinarySearch(target);
			idx = idx < 0 ? ~idx : idx;
			return Max(0, idx - 1);
		}

	}

}
namespace Nakov.IO {
	using System;
	using System.Text;
	using System.Globalization;

	public static class Cin {
		public static string NextToken() {
			StringBuilder tokenChars = new StringBuilder();
			bool tokenFinished = false;
			bool skipWhiteSpaceMode = true;
			while (!tokenFinished) {
				int nextChar = Console.Read();
				if (nextChar == -1) {
					tokenFinished = true;
				} else {
					char ch = (char)nextChar;
					if (char.IsWhiteSpace(ch)) {
						if (!skipWhiteSpaceMode) {
							tokenFinished = true;
							if (ch == '\r' && (Environment.NewLine == "\r\n")) {
								Console.Read();
							}
						}
					} else {
						skipWhiteSpaceMode = false;
						tokenChars.Append(ch);
					}
				}
			}

			string token = tokenChars.ToString();
			return token;
		}

		public static int NextInt() {
			string token = Cin.NextToken();
			return int.Parse(token);
		}
		public static long NextLong() {
			string token = Cin.NextToken();
			return long.Parse(token);
		}
		public static double NextDouble(bool acceptAnyDecimalSeparator = true) {
			string token = Cin.NextToken();
			if (acceptAnyDecimalSeparator) {
				token = token.Replace(',', '.');
				double result = double.Parse(token, CultureInfo.InvariantCulture);
				return result;
			} else {
				double result = double.Parse(token);
				return result;
			}
		}
		public static decimal NextDecimal(bool acceptAnyDecimalSeparator = true) {
			string token = Cin.NextToken();
			if (acceptAnyDecimalSeparator) {
				token = token.Replace(',', '.');
				decimal result = decimal.Parse(token, CultureInfo.InvariantCulture);
				return result;
			} else {
				decimal result = decimal.Parse(token);
				return result;
			}
		}

	}
}