import Foundation

var nAndMArr: [Int] = readLine()!.components(separatedBy: " ").map { Int($0)! }

let n = nAndMArr[0]
let m = nAndMArr[1]

var arr: [Int64] = Array(repeating: 0, count: n + 1)

for x in 1...m {
    let aBKArr = readLine()!.components(separatedBy: " ").map{ Int($0)! }
    let a: Int = aBKArr[0]
    let b: Int = aBKArr[1]
    let k: Int = aBKArr[2]
    
    arr[a-1] += k
    arr[b] -= k
}

var sum: Int64 = 0
var maximum: Int64 = 0

for y in 0..<n {
    sum += arr[y]
    maximum = max(sum, maximum)
}

print(maximum)