#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define drep(i, cc, n) for (ll i = (cc); i <= (n); ++i)
#define rep(i, n) drep(i, 0, n - 1)
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define fi first
#define se second

const ll MOD = 1000000007;
const ll MOD2 = 998244353;
const ll INF = 1LL << 60;
const ll MAX_N = 2e5;

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    
    ll h, w, k; cin >> h >> w >> k;
    ll ans = 0;
    rep(i, k){
        ll x, y, v; cin >> x >> y >> v;
        
        ll sa = (x+1)*x/2 + x*(x-1)/2;
        ll lx = 1 + x - y;
        if(lx > 1){
            sa -= lx*(lx-1)/2;
        }

        ll rx = 1 + x - (w-y+1);
        if(rx>1){
            sa -= rx*(rx-1)/2;
        }

        sa %= MOD2;
        ans += (sa * v)%MOD2;
        ans %= MOD2;
    }

    cout << ans << endl;
}