h, w, k = map(int, input().split())
w2 = 2 * w
d = [[0] * w2 for _ in range(h)]
for _ in range(k):
    x, y, v = map(int, input().split())
    d[x-1][w + y-1] = v
for i in range(1, h)[::-1]:
    for j in range(1, w2)[::-1]:
        d[i-1][j-1] += d[i][j]
for i in range(1, h)[::-1]:
    for j in range(w2 - 1):
        d[i-1][j+1] += d[i][j]
ans = 0
for i in range(h):
    for j in range(w):
        ans += d[i][w + j]
        if i + 1 < h:
            ans += d[i+1][w + j]
    ans %= 998244353
print(ans % 998244353)