from sys import stdin

if __name__ == '__main__':
    (N, M) = [int(i) for i in stdin.readline().split()]

    vals = [0] * N

    for i in range(M):
        (a, b, k) = [int(i) for i in stdin.readline().split()]
        vals[a-1] += k
        try:
            vals[b] -= k
        except:
            # out of range of list (at the end)
            pass

    prev = 0
    for i in range(len(vals)):
        prev += vals[i]
        vals[i] = prev

    print(max(vals))