package main

import (
    "fmt"
    "os"
    "bufio"
)

const MinInt = -(int(^uint(0) >> 1)  - 1) 

func main() {
    var n, m, a, b, k int
  
    io := bufio.NewReader(os.Stdin)
    fmt.Fscan(io, &n)
    fmt.Fscan(io, &m)
    l := make([]int, n)
    
    for i := 1; i <= m; i++ {
        fmt.Fscan(io, &a)
        fmt.Fscan(io, &b)
        fmt.Fscan(io, &k)
        
        l[a-1] += k
        if b <= n -1 {
            l[b] -= k
        }
    }
    
    max := MinInt
    sum := 0
    for _,v := range l {
        sum += v
        if sum >= max {
            max = sum
        }
    }
    fmt.Print(max)  
}