def f(a,b):
    if a>b:
        return 0
    n=b-a+1
    return (n*(b+a))//2

def solve():
    H,W,K=map(int,input().split())

    Ans=0; Mod=998244353
    for k in range(K):
        x,y,v=map(int,input().split())

        p=y-1; q=W-y
        area=x*W-(f(max(1,p-(x-1)),p)+f(max(1,q-(x-1)),q))%Mod
        Ans+=area*v%Mod

    return Ans%Mod
#==================================================
import sys
input=sys.stdin.readline
write=sys.stdout.write

print(solve())