H,W,N=map(int, input().split())
ans=0
mod=998244353
for i in range(N):
  h,w,p=map(int, input().split())
  c=(1+2*h-1)*h//2
  l=max(h-w,0)
  r=max(h-(W-w+1),0)
  ll,rr=l*(l+1)//2,r*(r+1)//2
  ans+=(c-ll-rr)*p
  ans%=mod
print(ans)