#include<bits/stdc++.h>
using namespace std;
#include<atcoder/all>
using namespace atcoder;
using ll = long long;
using mint = modint998244353;
ll h,w,n;
vector<ll> x,y,v;

void solve(){
	mint ans = 0;
	for(int i =0 ;i<n;i++){
		mint keisu = mint(x[i])*mint(x[i]);
		ll lh = x[i]-y[i];
		lh = max(0ll,lh);
		ll rh = x[i]-(w-y[i]+1);
		rh = max(0ll,rh);
		//cout<<keisu.val()<<' '<<lh<<' '<<rh<<' ';
		keisu -= (rh*(rh+1)/2);
		keisu -= (lh*(lh+1)/2);
		ans += keisu*v[i];
	}
	cout<<ans.val()<<endl;
}

signed main(){
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	cin >> h >> w >> n;
	x = y = v = vector<ll>(n);
	for(int i = 0;i<n;i++){
		cin >> x[i] >> y[i] >> v[i];
	}
	solve();
}