#include <iostream>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <iomanip>
#include <queue>
#include <algorithm>
#include <numeric>
#include <deque>
#include <complex>
#include <cassert>

using namespace std;
using ll = long long;

const ll modc = 998244353;

ll f(ll x, ll n){
    return ((x * (n+1)) % modc - (n * (n+1) / 2) % modc + modc) % modc;
}

int main(){

    ll H, W, K, x, y, v, ans=0;
    cin >> H >> W >> K;

    for (int i=0; i<K; i++){
        cin >> x >> y >> v;
        ans += ((f(x, min(y-1, x)) + f(x, min(W-y, x)) + modc - x) % modc) * v % modc;
        ans %= modc;
    }

    cout << ans << endl;

    return 0;
}