#include <iostream>
#include <vector>
#include <map>
using namespace std;
typedef long long ll;

ll mod = 998244353;

ll GridCount(ll W, ll x, ll y){
    ll ret = 0;
    if (x <= y){
        ret += x * (x + 1) / 2;
    }
    else{
        ret += (x * (x + 1) / 2 - (x - y) * (x - y + 1) / 2);
    }

    if (x <= W - y + 1){
        ret += x * (x + 1) / 2;
    }
    else{
        ret += (x * (x + 1) / 2 - (x - (W - y + 1)) * (x - (W - y + 1) + 1) / 2);
    }
    ret -= x;
    return ret;
}

int main(){
    ll H,W,K;
    cin >> H >> W >> K;
    vector<ll> x(K);
    vector<ll> y(K);
    vector<ll> v(K);
    for (ll i = 0; i < K; i++){
        cin >> x[i] >> y[i] >> v[i];
    }
    ll ans = 0;
    for (ll i = 0; i < K; i++){
        ll grid_count = GridCount(W, x[i], y[i]) % mod;
        grid_count = (grid_count * v[i]) % mod;
        ans = (ans + grid_count) % mod;
    }
    cout << ans << endl;
}