H, W, K = map(int, input().split())
ans = 0
mod = 998244353

def calc(x, y):
    ret = 0
    if x <= y:
        ret += x * (x + 1) // 2
    else:
        ret += (x * (x + 1) // 2 - (x - y) * (x - y + 1) // 2)

    if x <= W - y + 1:
        ret += x * (x + 1) // 2
    else:
        ret += (x * (x + 1) // 2 - (x - (W - y + 1)) * (x - (W - y + 1) + 1) // 2)
    ret -= x
    return ret

for i in range(K):
    x, y, v = map(int, input().split())
    C = calc(x, y) % mod
    ans = (ans + C * v) % mod
print(ans)