import os
import sys
from io import BytesIO, IOBase

BUFSIZE = 8192


class FastIO(IOBase):
	newlines = 0
	
	def __init__(self, file):
		self._fd = file.fileno()
		self.buffer = BytesIO()
		self.writable = "x" in file.mode or "r" not in file.mode
		self.write = self.buffer.write if self.writable else None
	
	def read(self):
		while True:
			b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
			if not b:
				break
			ptr = self.buffer.tell()
			self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
		self.newlines = 0
		return self.buffer.read()
	
	def readline(self):
		while self.newlines == 0:
			b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
			self.newlines = b.count(b"\n")+(not b)
			ptr = self.buffer.tell()
			self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
		self.newlines -= 1
		return self.buffer.readline()
	
	def flush(self):
		if self.writable:
			os.write(self._fd, self.buffer.getvalue())
			self.buffer.truncate(0), self.buffer.seek(0)


class IOWrapper(IOBase):
	def __init__(self, file):
		self.buffer = FastIO(file)
		self.flush = self.buffer.flush
		self.writable = self.buffer.writable
		self.write = lambda s:self.buffer.write(s.encode("ascii"))
		self.read = lambda:self.buffer.read().decode("ascii")
		self.readline = lambda:self.buffer.readline().decode("ascii")


sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
input = lambda:sys.stdin.readline().rstrip("\r\n")


mod = 998244353
h,w,k = map(int,input().split())
a = [[0] * w for i in range(h)]

# -t + w+1 = y
# t = w+1-y

# -t +1 = -y
# t = y+1

ans = 0
for i in range(k):
	x,y,v = map(int,input().split())
	#print(x-w-1+y, x-y)
	ans += x * x % mod * v
	ans %= mod
	if x-w-1+y > 0:
		ans -= max(0, (x-w-1+y) * (x-w+y) // 2) * v
		ans %= mod
	if x-y > 0:
		ans -= max(0, (x-y) * (x-y+1) // 2) * v
		ans %= mod
	#print(ans)

print(ans)