#include<iostream>
#include<set> 
#include<algorithm>
#include<vector>
#include<string>
#include<set>
#include<map>
#include<numeric>
#include<queue>
#include<cmath>
#include <unordered_set>
using namespace std;
typedef long long ll;
const ll INF=1LL<<60;
typedef pair<int,int> P;
typedef pair<int,P> PP;
const ll MOD=998244353;


ll mod_pow(ll x,ll y,ll mod){

    ll res=1;

    while(y>0){
        if(y&1){
            res*=x;
            res%=mod;
        }
        x*=x;
        x%=mod;
        y/=2;
    }
    return res;
}

int main(){
    int H,W,K;
    cin>>H>>W>>K;
    
    vector<int> x(K),y(K);
    vector<ll> v(K);
    for(int k=0;k<K;k++){
        cin>>x[k]>>y[k]>>v[k];
    }

    ll inv2=mod_pow(2,MOD-2,MOD);

   
    auto cumsum=[&](ll n){
        //1+2+3+...+n
        ll res=n%MOD;
        res*=(n+1)%MOD;

        res%=MOD;
        
        res*=inv2;
        
        res%=MOD;
        return res;
    };

    //[l,r]
    auto cumdif=[&](ll l,ll r){

        ll res=cumsum(r);
        if(l>=1){
            res-=cumsum(l-1);
            res+=MOD;
            res%=MOD;
        }
        return res;

    };

    //タカラが(px,py)にある

    auto f=[&](ll px,ll py){
        ll t=px+py;
        ll u=px-py;
        
        ll lb=max(1LL,1-u);

        ll c1=cumdif(lb,py);//[lb,py]
        c1+=u*(py-lb+1)%MOD;
        c1%=MOD;


        ll ub=min(1LL*W,t-1);
    
        ll len=ub;
        len-=(py-1+MOD)%MOD;
        len+=MOD;
        len%=MOD;

        ll c2=t*len%MOD;


        c2-=cumdif(py,ub);//[py,ub]
        c2+=MOD;
        c2%=MOD;

        ll res=(c1+c2)%MOD;

        res-=(px)%MOD;
        res+=MOD;
        res%=MOD;
        

        return res;
    };
    

    ll ans=0;
    for(int k=0;k<K;k++){
        ans+=v[k]*f(x[k],y[k])%MOD;
        ans%=MOD;
    }

    cout<<ans<<endl;


}