一日一プロ

using System;
using System.Collections.Generic;

namespace atcoder3
{
	public struct iseki
	{
		public int l, r, s;

	}

	class MainClass
	{
		public static void Main (string[] args)
		{
			var list = new List<iseki>();

			//Input
			string[] str = Console.ReadLine ().Split (' ');
			int N = int.Parse (str [0]);
			int M = int.Parse (str [1]);

			for (int i = 0; i < N; i++) {
				str = Console.ReadLine ().Split (' ');
				iseki tmp;
				tmp.l = int.Parse (str [0]);
				tmp.r = int.Parse (str [1]);
				tmp.s = int.Parse (str [2]);
				list.Add (tmp);
			}

			//Calc
			int[] sum = new int[M];
			for (int i = 0; i < M; i++) {
				sum [i] = 0; //Initialize
			}

			for (int i = 0; i < M; i++) {
				for (int j = 0; j < list.Count; j++) {
					if (list [j].l <= (i+1) && list [j].r >= (i+1)) {
						; //NoCount;
					} else {
						sum [i] += list [j].s;
					}
				}
			}

			int max = 0;
			for (int i = 0; i < M; i++) {
				if (max < sum [i]) {
					max = sum [i];
				}
			}
			Console.WriteLine ("{0}",max);
		}
	}
}