#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
using mint = modint998244353;
const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A& a, const B& b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A& a, const B& b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	long long h, w, k; cin >> h >> w >> k;
	vector<long long>x(k), y(k), v(k);
	rep(i, k) {
		cin >> x[i] >> y[i] >> v[i];
		x[i]--, y[i]--;
	}
	mint inv2 = ((mint)2).inv();
	mint ans = 0;
	rep(i, k) {
		long long f0 = x[i] - y[i] + 1;
		long long fx = x[i] + 1;
		long long fw = x[i] - (w - 1 - y[i]) + 1;
		mint sub = 0;
		if (f0 < 0) sub += (1 + fx) * fx * inv2;
		else sub += (f0 + fx) * (fx - f0 + 1) * inv2;
		if (fw < 0) sub += (1 + fx) * fx * inv2;
		else sub += (fw + fx) * (fx - fw + 1) * inv2;
		sub -= fx;
		ans += sub * v[i];
	}
	cout << ans.val() << endl;
	return 0;
}