#include <bits/stdc++.h>
using namespace std;
using ll = long long;
ll calc(ll H, ll W, ll r, ll c) {
    ll L, R;
    ll b = 0;
    if (r + c >= 2 && r >= c) {
        L = c - 1;
        b += max(0ll, r - c);
    } else {
        L = r - 1;
    }
    if (r + c >= 1 + W && r - c >= 1 - W) {
        R = W - c;
        b += max(0ll, r - 1 - (W - c));
    } else {
        R = r - 1;
    }
    ll s = (L + R) * (r - 1) * 2 - L * L - R * R;
    b += (L + R + 1) * 2 - 2;
    ll a = (s - b + 1) / 2;
    return a + b;
}
ll const m = 998244353;
int main () {
    ll H, W, K;
    cin >> H >> W >> K;
    ll ans = 0;
    for (int i = 0; i < K; i ++) {
        ll x, y, v;
        cin >> x >> y >> v;
        v %= m;
        ll c = calc(H, W, x, y) % m;
        ans += (c * v) % m;
        ans %= m;
    }
    cout << ans << endl;
}