H,W,K=map(int,input().split())
mod=998244353

ANS=0
for i in range(K):
    x,y,v=map(int,input().split())

    ANS+=x*v

    r=W-y
    if r<x-1:
        ANS+=(r*x-r*(r+1)//2)*v
    else:
        ANS+=((x-1)*x//2)*v
     
    l=y-1
    if l<x-1:
        ANS+=(l*x-l*(l+1)//2)*v
    else:
        ANS+=((x-1)*x//2)*v

    ANS%=mod

print(ANS)