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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.util.HashMap;
import java.io.IOException;
import java.util.BitSet;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author Washoum
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        inputClass in = new inputClass(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        DRecording solver = new DRecording();
        solver.solve(1, in, out);
        out.close();
    }

    static class DRecording {
        static DRecording.Subset[] subsets;

        static int find(int i) {
            if (subsets[i].parent != i)
                subsets[i].parent = find(subsets[i].parent);
            return subsets[i].parent;
        }

        static void union(int x, int y) {
            int xroot = find(x);
            int yroot = find(y);

            if (subsets[xroot].rank < subsets[yroot].rank)
                subsets[xroot].parent = yroot;
            else if (subsets[yroot].rank < subsets[xroot].rank)
                subsets[yroot].parent = xroot;
            else {
                subsets[xroot].parent = yroot;
                subsets[yroot].rank++;
            }
        }

        public void solve(int testNumber, inputClass sc, PrintWriter out) {
            int n = sc.nextInt();
            int c = sc.nextInt();
            BitSet[] rep = new BitSet[c];
            for (int i = 0; i < c; i++) {
                rep[i] = new BitSet(100001);
            }
            for (int i = 0; i < n; i++) {
                int s = sc.nextInt();
                int t = sc.nextInt();
                int ch = sc.nextInt() - 1;
                rep[ch].set(s, t + 1);
            }
            subsets = new DRecording.Subset[c];
            for (int i = 0; i < c; i++) {
                subsets[i] = new DRecording.Subset();
                subsets[i].parent = i;
                subsets[i].rank = 0;
                subsets[i].b = rep[i];
            }
            for (int i = 0; i < c; i++) {
                for (int j = i + 1; j < c; j++) {
                    int g1 = find(i);
                    int g2 = find(j);
                    if (g1 != g2) {
                        BitSet tmp = new BitSet(100001);
                        tmp.or(subsets[g1].b);
                        tmp.and(subsets[g2].b);
                        if (tmp.cardinality() == 0) {
                            union(i, j);
                            int g = find(i);
                            BitSet r = new BitSet(100001);
                            r.or(subsets[g1].b);
                            r.or(subsets[g2].b);
                            subsets[g].b = r;
                        }
                    }
                }
            }
            HashMap<Integer, Integer> map = new HashMap<>();
            for (int i = 0; i < c; i++) {

                map.put(find(i), 1);
            }
            out.println(map.size());
        }

        static class Subset {
            int parent;
            int rank;
            BitSet b;

        }

    }

    static class inputClass {
        BufferedReader br;
        StringTokenizer st;

        public inputClass(InputStream in) {

            br = new BufferedReader(new InputStreamReader(in));
        }

        public String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

    }
}