#include <bits/stdc++.h>
#include<iostream>
#include<map>
#include<vector>
#include <algorithm>
#include<math.h>
#include <iomanip>
#include<set>
#include <numeric>
#include<string>
using ll = long long;
using namespace std;


int main()
{
    ll h, w, k, sum1 = 0, mod = 998244353;
    cin >> h >> w >> k;
    for (ll i = 0; i < k; i++){
        ll x, y, v, dl, dr;
        cin >> x >> y >> v;
        dl = max(x - y, (ll) 0);
        dr = max(x - (w - y + 1), (ll) 0);
        sum1 += (x*x - (dl+1)*dl/2 - (dr+1)*dr/2)*v;
        sum1 %= mod;
    }
    cout << sum1 << endl;
}