#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001

using P = pair<mint,mint>;
P op(P a,P b){
	a.first += b.first;
	a.second += b.second;
	return a;
}

P e(){
	return make_pair(0,0);
}

P mapping(mint a,P b){
	b.first += a*b.second;
	return b;
}

mint composition(mint a,mint b){
	return a+b;
}

mint id(){
	return 0;
}

int main(){
	
	int H,W,K;
	cin>>H>>W>>K;
	vector<P> t(300000,make_pair(0,1));
	
	vector<lazy_segtree<P,op,e,mint,mapping,composition,id>> seg(2,
	lazy_segtree<P,op,e,mint,mapping,composition,id>(t));
	
	int C = 100001;
	vector<vector<pair<int,long long>>> vs(C*2);
	rep(i,K){
		int x,y,z;
		cin>>x>>y>>z;
		x--,y--;
		vs[x-y+C].emplace_back(x+y,z);
	}
	mint ans = 0;
	rep(i,C*2){
		int tt = i-C;
		int L=max(tt,-tt),R = min(2*(W-1)+tt,2*(H-1)-tt);
		if(L<=R){
			seg[L%2].apply(L/2,R/2+1,1);
		}
		rep(j,vs[i].size()){
			int y = vs[i][j].first;
			mint vv = vs[i][j].second;
			mint s = 0;
			if(y%2==0){
				s += seg[0].prod(0,y/2+1).first;
				s += seg[1].prod(0,y/2).first;
			}
			else{
				s += seg[0].prod(0,y/2+1).first;
				s += seg[1].prod(0,y/2+1).first;
			}
			ans += vv * s;
		}
	}
	cout<<ans.val()<<endl;
	
	return 0;
}