#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<ll,ll> P;
#define REP(i,n) for(int i=0;i<int(n);i++)

const ll MOD=998244353;
ll x[200010],y[200010],v[200010];

int main(void){
	cin.tie(nullptr);  ios_base::sync_with_stdio(false);
	int i,j,k;

	ll H,W,K;
	cin >> H >> W >> K;

	for(i=1;i<=K;i++) cin >> x[i] >> y[i] >> v[i];

	ll ans=0;
	for(i=1;i<=K;i++){
		ll a=x[i],b=y[i];
		ll s=a*a;
		if(a+b-W>=2) s-=(a+b-W-1)*(a+b-W)/2;
		if(a-b>=1) s-=(a-b+1)*(a-b)/2;

		ans+=s*v[i];
		ans%=MOD;
	}

	cout << ans << endl;


	return 0;
}