H,W,K=map(int,input().split())
def cnt(x,y):
    retu=(x+1)**2
    if x-y>0:
        retu-=(x-y)*(x-y+1)//2
    if x+y-(W-1)>0:
        retu-=(x+y-(W-1))*(x+y-(W-1)+1)//2
    return retu
ans=0
mod=998244353
for k in range(K):
    x,y,v=map(int,input().split())
    x-=1;y-=1
    ans+=v*cnt(x,y)
ans%=mod
print(ans)