#include <iostream>
#include <atcoder/modint>
using namespace std;
using mint = atcoder::modint998244353;
using lint = long long;

int main() {
    cin.tie(nullptr), ios::sync_with_stdio(false);
    lint H, W;
    int K;
    cin >> H >> W >> K;
    mint ret = 0;
    while (K--) {
        lint x, y, v;
        cin >> x >> y >> v;
        lint lo = max<lint>(1, y - (x - 1)), wlo = x - abs(y - lo);
        lint hi = min<lint>(W, y + (x - 1)), whi = x - abs(y - hi);
        mint cnt = (wlo + x) * (y - lo + 1) / 2 + (whi + x) * (hi - y + 1) / 2 - x;
        ret += cnt * v;
    }
    cout << ret.val() << endl;
}