#include<bits/stdc++.h>
using namespace std;

#define INF 1234567890
#define ll long long
#define MOD 998244353

ll res = 0;
int N, M, K;

int main()
{
	ios::sync_with_stdio(0); cin.tie(0);
	cin.exceptions(ios::badbit | ios::failbit);
	cin >> N >> M >> K;
	vector<array<int, 3> > v;
	vector<pair<int, int> > q;
	for(int i=0; i<K; i++)
	{
		int y, x, val;
		cin >> y >> x >> val;
		ll cnt = y-1, L = x, R = x;
		ll sum = 1;

		// case 1
		if (cnt > 0)
		{
			ll k = min({cnt, L-1, M-R});
			sum += ((k+1)*(k+1) - 1), sum %= MOD;
			cnt -= k;
			L -= k;
			R += k;
		}

		// case 2
		if (cnt > 0 && (L-1 > 0 || M-R > 0))
		{
			ll k = min({cnt, (L-1 > 0 ? L-1 : INF), (M-R > 0 ? M-R : INF)});
			sum += ((R-L+1)*k + k*(k+1)/2), sum %= MOD;
			cnt -= k;
		}

		// case 3
		if (cnt > 0)
		{
			sum += cnt*M, sum %= MOD;
		}

		res += sum * val, res %= MOD;
	}
	res %= MOD; res += MOD; res %= MOD;
	cout << res << "\n";
	return 0;
}