object Solution {
    def main(args: Array[String]) = {
    val scan = new java.util.Scanner(System.in)
    val n  = scan.nextInt()
    val m = scan.nextInt()

    val arr:Array[Long] = Array.fill(n)(0)

    var  lower: Int =0
    var upper:Int =0
    var sum:Long=0
    for{
      i <- 0 until m
    }{
            lower=scan.nextInt()
            upper=scan.nextInt()
            sum=scan.nextInt()
            arr.update(lower-1,arr(lower-1)+sum)
            if(upper<n)
              arr.update(upper,(arr(upper)-sum))
    }

    var max: Long = 0;
    var temp:  Long = 0;

    for{
      i <- 0 until n
    }{
      temp = temp+arr(i)
      if(temp>max) max=temp
    }

    System.out.println(max)
  }
}