#include <bits/stdc++.h>

using namespace std;

const int mod = 998244353;
// const int mod = 1000000007;
struct modint {
    long long a = 0;
    modint(long long x = 0) {while (x < 0) x += mod; a = x % mod;}
    modint(const modint &r) {a = r.a;}
    modint operator -(){return modint(-a);}
    modint operator +(const modint &r) {return modint(*this) += r;}
    modint operator -(const modint &r) {return modint(*this) -= r;}
    modint operator *(const modint &r) {return modint(*this) *= r;}
    modint &operator +=(const modint &r) {
      a += r.a;
      if(a >= mod) a -= mod;
      return *this;
    }
    modint &operator -=(const modint &r) {
        a -= r.a;
        if(a < 0) a += mod;
        return *this;
    }
    modint &operator *=(const modint &r) {
        a = a * r.a % mod;
        return *this;
    }
    modint pow(long long r) const {
        if (!r) return 1;
        modint x = pow(r >> 1);
        x *= x;
        if (r & 1) x *= *this;
        return x;
    }
    modint inverse() const {
        return pow(mod - 2);
    }
    modint& operator/=(const modint r) {
        return (*this) *= r.inverse();
    }
    modint operator/(const modint r) const {
        modint res(*this);
        return res /= r;
    }
};
 
istream &operator>>(istream &is, modint &x) {
    long long t;
    is >> t;
    x = t;
    return is;
}
ostream &operator<<(ostream &os, const modint& x) {
    return os << x.a;
}
const int MAX = 500044;
modint fac[MAX], inv[MAX], finv[MAX];
void cominit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for(int i = 2; i < MAX; i++) {
        fac[i] = fac[i - 1] * modint(i);
        inv[i] = - inv[mod % i] * modint(mod / i);
        finv[i] = finv[i - 1] * inv[i];
    }
}
modint Com(long long n, long long k) {
    if(n < k) return 0;
    if(n < 0 || k < 0) return 0;
    return fac[n] * finv[k] * finv[n - k];
}
modint Per(long long n, long long k) {
    if(n < k) return 0;
    if(n < 0 || k < 0) return 0;
    return fac[n] * finv[n - k];
}
 
using Mint = modint;

int main() {
    int h, w, k;
    cin >> h >> w >> k;
    vector<int> x(k), y(k), v(k);
    for (int i = 0; i < k; i++) {
        cin >> x[i] >> y[i] >> v[i];
    }
    Mint ans = 0;
    for (int i = 0; i < k; i++) {
        long long A = max(1, x[i] - y[i] + 1);
        Mint B = (A + x[i]) * (x[i] - A + 1) / 2;
        long long C = max(1, x[i] - (w - y[i]));
        Mint D = (C + x[i]) * (x[i] - C + 1) / 2;
        ans += Mint(v[i]) * Mint(B + D - x[i]);
    }
    cout << ans << endl;
}