import java.io.*;

import java.math.*;

import java.security.*;

import java.text.*;

import java.util.*;

import java.util.concurrent.*;

import java.util.regex.*;

public class Testing{

public static void main(String[] args){

Scanner sc = new Scanner(System.in);

int n = sc.nextInt();

long m = sc.nextLong();

long arr[] = new long[n];

for(int j = 1 ; j <= m ; j++){

int a = sc.nextInt();

int b = sc.nextInt();

int k = sc.nextInt();

arr[a] += k;

if(b < n){

arr[b+1] -= k;

}

}

long sum = arr[1];

long max = arr[1];

for(int i = 2; i < n + 1 ; i++){

sum =sum + arr[i];

if(max < sum){

max = sum;

}

}

System.out.println(max);

}

}