h,w,k = map(int,input().split())
mod = 998244353; ans = 0
for _ in range(k):
    x,y,v = map(int,input().split())
    ans += ((max(x-y+1,1)+x)*min(x,y)//2+(x-1+max(x-w+y,1))*min(x-1,w-y)//2)*v%mod
print(ans%mod)