mod = 998244353


def main():
    import sys
    input = sys.stdin.readline

    def f(h):
        h += 1
        return h * (h + 1) // 2

    H, W, K = map(int, input().split())
    ans = 0
    for _ in range(K):
        h, w, v = map(int, input().split())
        h -= 1
        w -= 1
        tmp = ((h + 1) * (h + 1)) % mod
        h1 = h - w - 1
        if h1 >= 0:
            tmp = (tmp - f(h1)) % mod
        h2 = h - (W - w)
        if h2 >= 0:
            tmp = (tmp - f(h2)) % mod
        ans = (ans + tmp * v) % mod
    print(ans)


if __name__ == '__main__':
    main()