#include<bits/extc++.h>
#include<atcoder/modint>
using namespace __gnu_pbds;
using namespace std;
using namespace atcoder;
using ll = long long;
using ull = unsigned long long;
using Mint = modint998244353;
using mint = modint;
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define rrep(i, n) for (int i = (int)(n)-1; i >= 0; --i)
#define rep2(i, a, b) for (int i = (int)a; i < (int)(b); ++i)
#define rrep2(i, a, b) for (int i = (int)(b)-1; i >= (int)(a); --i)
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
constexpr int dx[] = {-1,0,1,0};
constexpr int dy[] = {0,-1,0,1};
constexpr int MAX_N = 100000;
//ダイクストラ法：makedijkstra
//エラトステネスの篩：makesieve
//テストケースが複数の場合：multest

int main(){
    //cin.tie(nullptr);
    //std::ios_base::sync_with_stdio(false);
    int H, W, total_testcases;
    scanf("%d %d %d", &H, &W, &total_testcases);
    auto add = [&](int x, int y){
        bool right = x + y > W + 1;
        bool left = x > y;
        return (right ? (ll)x*(W - y + 1) - (ll)(W - y + 1)*(W - y)/2 : (ll)x*(x+1)/2)
            + (left ? (ll)x*y - (ll)y*(y-1)/2 : (ll)x*(x+1)/2)
            - x;
    };
    Mint ans{0};
    for (int testcase_i = 1; testcase_i <= total_testcases; ++testcase_i){
        int x, y, v;
        scanf("%d %d %d", &x, &y, &v);
        ans += Mint(add(x, y))*Mint(v);
    }
    printf("%u\n", ans.val());
    return 0;
}