MOD = 998244353

H, W, K = map(int, input().split())
total = 0

for _ in range(K):
    x, y, v = map(int, input().split())
    s = x + y
    t = x - y
    cnt = 0
    for i in range(1, H + 1):
        lower = max(1, i - t)
        upper = min(s - i, W)
        if upper >= lower:
            cnt += upper - lower + 1
    total = (total + v * cnt) % MOD

print(total)