#include <bits/stdc++.h>
#include <atcoder/all>
// url https://yukicoder.me/problems/no/2229
#define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=b-1;i>=a;i--)
#define all(x) (x).begin(),(x).end()
#define pb(x) push_back(x);
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a = b; return 1; } return 0; }
typedef long long ll;
typedef long double lld;
using namespace std;
using namespace atcoder;
using mint = static_modint<998244353>;
// using mint = static_modint<1000000007>;
const ll mod=998244353;
//const ll mod=1e9+7;
int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};
const string zton="0123456789";
const string atoz="abcdefghijklmnopqrstuvwxyz";
const string ATOZ="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const ll inf=(1ll<<60);
// const int inf=(1<<30);
lld dist(lld x1,lld x2,lld y1,lld y2){
    lld res=(x1-x2)*(x1-x2)+(y1-y2)*(y1-y2);
    res=sqrt(abs(res));
    return res;
}
lld arg(lld x,lld y){
    const lld eps=1e-8;
    lld res=0;
    if(abs(x)+abs(y)<=eps)return 0.0;
    else if(abs(x)<=eps){
        if(y>=0.0)return (M_PI/2);
        else return (M_PI/2+M_PI);
    }
    else if(abs(y)<=eps){
        if(x>=0.0)return 0.0;
        else return M_PI;
    }
    res=atan2(abs(y),abs(x));
    if(x<=0&&y>=0)res=(M_PI-res);
    else if(x<=0&&y<=0)res+=(M_PI);
    else if(x>=0&&y<=0)res=(M_PI*2-res);
    return res;
}
ll gcd(ll a,ll b){
    if(a==0||b==0)return a+b;
    ll r;
    r=a%b;
    if(r==0){
        return b;
    }
    else{
        return gcd(b,r);
    }
}
typedef pair<ll,int> P;

int main(void){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int H,W,K;cin >> H >> W >> K;
    vector<int> x(K),y(K);
    vector<ll>  v(K);
    rep(i,0,K){
        cin >> x[i] >> y[i] >> v[i];
        x[i]--;y[i]--;
        x[i]=H-1-x[i];
        // y[i]=W-1-y[i];
    }
    mint ans=0;
    rep(k,0,K){
        ll tmp=0;
        int l=x[k]+y[k];
        int r=W-1+x[k]-y[k];
        // cout << k << " " << l << " " << r << endl;
        if(l>=H-1&&r>=H-1){
            ll n=H-x[k];
            ll a1=1;
            ll an=n*2-1;
            tmp=(a1+an)*n/2;
        }
        else{
            ll n1=H-x[k];
            ll a1=1;
            ll an=n1*2-1;
            tmp+=(a1+an)*n1/2;
            ll n2=H-l-1;
            ll b2=(n2*(n2+1)/2);
            ll n3=H-r-1;
            ll b3=(n3*(n3+1)/2);
            if(n2>=0){
                tmp-=b2;
            }
            if(n3>=0){
                tmp-=b3;
            }
            // cout << n1 << " " << n2 << " " << n3 << endl;
        }
        ans+=v[k]*tmp;
        // cout << tmp << endl;
    }
    cout << ans.val() << endl;
    // rep(i,0,H){
    //     rep(j,0,W){
    //         int l=i+j;
    //         int r=W-1+i-j;
    //         cout << i << " " << j << " " << l << " " << r << endl;
    //     }
    // }
}