MOD = 998244353

def main():
    import sys
    input = sys.stdin.read
    data = input().split()
    idx = 0
    H = int(data[idx]); idx +=1
    W = int(data[idx]); idx +=1
    K = int(data[idx]); idx +=1
    
    total = 0
    for _ in range(K):
        x = int(data[idx]); idx +=1
        y = int(data[idx]); idx +=1
        v = int(data[idx]); idx +=1
        
        s = x + y
        t = x - y
        
        res = 0
        
        # Case 1-1
        a = max(x - y + 1, x + y - W, 1)
        b = min(x, H, s - 1)
        if a <= b:
            n = b - a + 1
            A = 2 * x - 2 * a + 1
            B = 2 * x - 2 * b + 1
            res += n * (A + B) // 2
        
        # Case 1-2
        a = max(x - y + 1, 1)
        b = min(x + y - W - 1, x, H, s - 1)
        if a <= b:
            first = W + t + 1 - a
            last = W + t + 1 - b
            term = (first + last) * (b - a + 1) // 2
            res += term
        
        # Case 2-1
        a = max(x + y - W, 1)
        b = min(x - y, x + y - 1, H)
        if a <= b:
            first = s - a
            last = s - b
            term = (first + last) * (b - a + 1) // 2
            res += term
        
        # Case 2-2
        a = 1
        b = min(x + y - W - 1, x - y, H)
        if a <= b:
            res += W * (b - a + 1)
        
        res %= MOD
        total = (total + res * v) % MOD
    
    print(total % MOD)

if __name__ == "__main__":
    main()