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: Accepted)

#pragma warning disable

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.Serialization.Formatters.Binary;
using System.Text;
using System.Text.RegularExpressions;
using System.Diagnostics;
using System.Numerics;
using System.Collections;

static class MainClass
{
    public static void Main(string[] args)
    {
        var nc = Console.ReadLine().SplittedStringToInt32List();
        var n = nc[0];
        var c = nc[1];
        var channels = new int[c, 200010];

        for (int i = 0; i < n; i++)
        {
            var stc = Console.ReadLine().SplittedStringToInt32List();
            var ch = stc[2];
            var s = stc[0] - 1;
            var t = stc[1] - 1;
            channels[ch - 1, s*2 - 1 + 3] = 1;
            channels[ch - 1, t*2 + 3] = -1;
        }
        var treatedchs = new int[c, 200010];
        for (int i = 0; i < c; i++)
        {
            treatedchs[i, 0] = channels[i,0];
            for (int j = 0; j < 200010 - 1; j++)
            {
                treatedchs[i,j + 1] = treatedchs[i,j] + channels[i,j + 1];
            }
        }
        var maxcount = 0;

        for (int i = 0; i < 200010; i++)
        {
            var count = 0;

            for (int j = 0; j < c; j++)
            {
                if (treatedchs[j, i] > 0)
                    count++;
            }
            maxcount = Math.Max(maxcount, count);
        }
        Console.WriteLine(maxcount);
        Console.ReadLine();
        



        //var nm = Console.ReadLine().SplittedStringToInt32List();
        //var n = nm[0];
        //var m = nm[1];
        //InitializeUnionFind(n);
        //var abs = new List<KeyValuePair<int,int>>();
        //for (int i = 0; i < m; i++)
        //{
        //    var ab = Console.ReadLine().SplittedStringToInt32List();
        //    abs.Add(new KeyValuePair<int, int>(ab[0] - 1, ab[1] - 1));
        //}
        //abs.Reverse();
        //var ls = new List<int>();
        //foreach (var item in abs)
        //{
        //    Unite(item.Key, item.Value);
        //    ls.Add(ParentCount);
        //}
        //ls.Reverse();
        //var before = -1;
        //var befores = 0;
        //for (int i = 0; i < m; i++)
        //{
        //    if (before != -1)
        //    {
        //        var num = ls[i] - befores;
        //        Console.WriteLine((num * (num - 1))/2 + before);
        //        before = (num * (num - 1)) / 2 + before;
        //    }
        //    else
        //    {
        //        var num = ls[i] - befores;
        //        Console.WriteLine((num * ( num - 1)) / 2);
        //        before = (num * (num - 1)) / 2;
        //    }
        //    befores = ls[i];
        //}

        //Console.ReadLine();
    }


    public static List<List<int>> NBasedSearch(int n, int length)
    {
        if (length == 1)
        {
            var ls = new List<List<int>>();
            for (int i = 0; i < n; i++)
            {
                var lss = new List<int>();
                lss.Add(i);
                ls.Add(lss);
            }
            return ls;
        }
        else
        {
            var ans = NBasedSearch(n, length - 1);
            var news = new List<List<int>>();
            foreach (var item in ans)
            {
                for (int i = 0; i < n; i++)
                {
                    var based = item.ToList();
                    based.Add(i);
                    news.Add(based);
                }
            }
            return news;

        }
    }

    public static int ParentCount;

    public static int[] Parents;
    public static int[] IfParentsChildrenCount;

    public static int[] Ranks;

    public static void InitializeUnionFind(int N)
    {
        Parents = new int[N];
        Ranks = new int[N];
        IfParentsChildrenCount = new int[N];
        for (int i = 0; i < N; i++)
        {
            Parents[i] = i;
            Ranks[i] = 0;
            IfParentsChildrenCount[i] = 1;
        }
        ParentCount = N + 1;
    }

    public static int Root(int a)
    {
        if (Parents[a] == a)
        {
            return a;
        }
        else
        {
            Parents[a] = Root(Parents[a]);
            return Parents[a];
        }
    }

    public static bool Same(int a, int b)
    {
        return Root(a) == Root(b);
    }

    public static void Unite(int a, int b)
    {
        var parentA = Root(a);
        var parentB = Root(b);
        if (parentA == parentB)
            return;
        if (Ranks[parentA] < Ranks[parentB])
        {
            Parents[parentA] = parentB;
            IfParentsChildrenCount[parentB] += IfParentsChildrenCount[parentA];
            ParentCount -= IfParentsChildrenCount[parentA];

            IfParentsChildrenCount[parentA] = 0;
        }
        else
        {
            Parents[parentB] = parentA;
            if (Ranks[parentA] == Ranks[parentB])
            {
                Ranks[parentA]++;
            }
            IfParentsChildrenCount[parentA] += IfParentsChildrenCount[parentB];
            ParentCount -= IfParentsChildrenCount[parentB];
            IfParentsChildrenCount[parentB] = 0;
        }
    }



    public static int Manhattan(int x1, int x2, int y1, int y2)
    {
        return Math.Abs(x1 - x2) + Math.Abs(y1 - y2);
    }




    public static IEnumerable<IEnumerable<T>> Perm<T>(this IEnumerable<T> items, int? k = null)
    {
        if (k == null)
            k = items.Count();

        if (k == 0)
        {
            yield return Enumerable.Empty<T>();
        }
        else
        {
            var i = 0;
            foreach (var x in items)
            {
                var xs = items.Where((_, index) => i != index);
                foreach (var c in Perm(xs, k - 1))
                    yield return c.Before(x);

                i++;
            }
        }
    }


    public static IEnumerable<T> Before<T>(this IEnumerable<T> items, T first)
    {
        yield return first;

        foreach (var i in items)
            yield return i;
    }

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


    public static long Sums(IEnumerable<int> list)
    {
        var sum = 0l;
        foreach (var item in list)
        {
            sum += item;
        }
        return sum;
    }

    public static long f(long n, long b)
    {
        if (n < b)
        {
            return n;
        }
        else
        {
            return f((long)Math.Floor((double)n / b), b) + n % b;
        }
    }

    public static string N(long n, long b)
    {
        var sb = new StringBuilder();
        while (true)
        {
            sb.Append((n % b).ToString());
            n /= b;
            if (n < b)
            {
                sb.Append(n.ToString());
                break;
            }
        }
        return new string(sb.ToString().Reverse().ToArray());
    }


    public static BigInteger[] factors;
    public static BigInteger[] revFactors;
    public static void SetFactor(int N)
    {
        factors = new BigInteger[N];
        factors[0] = 1;
        revFactors = new BigInteger[N];
        for (int i = 1; i < N; i++)
        {
            factors[i] = factors[i - 1] * i;
            factors[i] %= Mod1e9;
        }
        revFactors[N - 1] = BigInteger.ModPow(factors[N - 1], Mod1e9 - 2, Mod1e9);
        for (int i = N - 2; i >= 0; i--)
        {
            revFactors[i] = revFactors[i + 1] * (i + 1);
            revFactors[i] %= Mod1e9;
        }
    }
    public static BigInteger GetCombination(int a, int b)
    {
        return (((factors[a] * revFactors[b]) % Mod1e9) * revFactors[a - b]) % Mod1e9;
    }

    #region ライブラリ
    public static long ToInt64(this string str) => long.Parse(str);
    public static int ToInt32(this string str) => int.Parse(str);
    public static BigInteger ToBigInteger(this string str) => BigInteger.Parse(str);
    public static List<string> SplittedStringToList(this string str) => str.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).ToList();
    public static List<int> SplittedStringToInt32List(this string str) => str.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).Select(x => int.Parse(x)).ToList();
    public static List<long> SplittedStringToInt64List(this string str) => str.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).Select(x => long.Parse(x)).ToList();
    public static List<BigInteger> SplittedStringToBigInteger(this string str) => str.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).Select(x => BigInteger.Parse(x)).ToList();
    public const int INF = int.MaxValue / 4;
    public const long LONGINF = long.MaxValue / 2;
    public const int Mod1e9 = 1000000007;

    public static void PrintArray(bool[,] array)
    {
        for (int i = 0; i < array.GetLength(0); i++)
        {
            var sb = new StringBuilder();
            for (int j = 0; j < array.GetLength(1); j++)
            {
                sb.Append(array[i, j]).Append(" ");
            }
            Console.WriteLine(sb.ToString());
        }
    }

    #endregion
}