/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		// your code goes here
		long k,q,s=0;
		int n,a,b,i;
		Scanner sc = new Scanner(System.in);
		n = sc.nextInt();
		q = sc.nextLong();
		long[] arr = new long[n+2];
 
		for(i=0;i<q;i++){
			a = sc.nextInt();
			b = sc.nextInt();
			k = sc.nextLong();
			arr[a] = arr[a] + k;
			arr[b+1] = arr[b+1] - k;
		}
		long max = Integer.MIN_VALUE;
		for(i=1;i<=n;i++){
			arr[i] = arr[i] + arr[i-1];
			max = Math.max(arr[i],max);
		}
		System.out.print(max);
	}
}

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NSAzCjEgMiAxMDAKMiA1IDEwMAozIDQgMTAw

5 3
1 2 100
2 5 100
3 4 100