using System.CodeDom.Compiler;
using System.Collections.Generic;
using System.Collections;
using System.ComponentModel;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Runtime.Serialization;
using System.Text.RegularExpressions;
using System.Text;
using System;

class Solution {

    // Complete the arrayManipulation function below.
    static long arrayManipulation(int n, int[][] queries) {
            long result=0;
            int[] answers;
            int tempCounter=0;
            // get every [y,2] element
            for(int y=0;y<queries.GetLength(0);y++){ // go through y rows
                for(int x=0;x<2;x++){// go through x rows skipping last element
                tempCounter=queries[y][0];
                    while(tempCounter>=queries[y][0]&&tempCounter<=queries[y][1]){
                        tempCounter++;
                        answers[tempCounter]+=queries[y][2];
                    }

                }
            }
            result=answers.Max();
            return result;

    }

    static void Main(string[] args) {
        TextWriter textWriter = new StreamWriter(@System.Environment.GetEnvironmentVariable("OUTPUT_PATH"), true);

        string[] nm = Console.ReadLine().Split(' ');

        int n = Convert.ToInt32(nm[0]);

        int m = Convert.ToInt32(nm[1]);

        int[][] queries = new int[m][];

        for (int i = 0; i < m; i++) {
            queries[i] = Array.ConvertAll(Console.ReadLine().Split(' '), queriesTemp => Convert.ToInt32(queriesTemp));
        }

        long result = arrayManipulation(n, queries);

        textWriter.WriteLine(result);

        textWriter.Flush();
        textWriter.Close();
    }
}