// Problem: No.2229 Treasure Searching Rod (Hard)
// Contest: yukicoder
// URL: https://yukicoder.me/problems/no/2229
// Memory Limit: 512 MB
// Time Limit: 2000 ms

#include <bits/stdc++.h>

#define fastio ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
#define dbg(x) cout << #x << " = " << (x) << "\n";
#define popcount(x) __builtin_popcountll((x))
#define all(v) (v).begin(), (v).end()
#define pb emplace_back
#define x first
#define y second

using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;

const int inf = 0x3f3f3f3f;
const int mod = 998244353;

struct mint {
  ll x;  // typedef long long ll;
  mint(ll x = 0) : x((x % mod + mod) % mod) {}
  mint operator-() const { return mint(-x); }
  mint& operator+=(const mint a) {
    if ((x += a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator-=(const mint a) {
    if ((x += mod - a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator*=(const mint a) {
    (x *= a.x) %= mod;
    return *this;
  }
  mint operator+(const mint a) const {
    mint res(*this);
    return res += a;
  }
  mint operator-(const mint a) const {
    mint res(*this);
    return res -= a;
  }
  mint operator*(const mint a) const {
    mint res(*this);
    return res *= a;
  }
  mint pow(ll t) const {
    if (!t) return 1;
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1) a *= *this;
    return a;
  }

  // for prime mod
  mint inv() const { return pow(mod - 2); }
  mint& operator/=(const mint a) { return (*this) *= a.inv(); }
  mint operator/(const mint a) const {
    mint res(*this);
    return res /= a;
  }
};
istream& operator>>(istream& is, mint& a) { return is >> a.x; }
ostream& operator<<(ostream& os, const mint& a) { return os << a.x; }

ll n, m, c;
mint calc(ll x, ll y) {
  mint mn = min(x, y) + 1;
  mint res = 0;
  res = res + (mint(1) + mn) * mn / mint(2);
  res = res + mint(y + 1) * mint(x - min(x, y));
  mint mn2 = min(x, m - y - 1);
  res = res + (mint(1) + mn2) * mn2 * mint(2).inv();
  res = res + mint(m - 1 - y) * mint(x - min(x, m - y - 1));
  return res;
}

void solve() {
  mint ans = 0;
  cin >> n >> m >> c;
  for (int i = 1; i <= c; i++) {
    int x, y;
    mint v;
    cin >> x >> y >> v;
    --x, --y;
    ans = ans + calc(x, y) * v;
  }
  cout << ans << "\n";
}

int main() {
  fastio;
  int t = 1;
  // cin >> t;
  while (t--) {
    solve();
  }
  return 0;
}