def main():
    h, w, k = map(int, input().split())
    ans = 0
    for _ in range(k):
        x, y, v = map(int, input().split())
        a = x*x
        z = max(0, x-y)
        a -= z*(z+1)//2
        z = max(0, x-(w+1-y))
        a -= z*(z+1)//2
        ans += a * v
    print(ans % 998244353)


if __name__ == '__main__':
    main()