#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using namespace std;
using ll=long long;
using ld=double;
ld pie=3.14159265359;
ll mod=998244353;
ll inf=100000;
int main(){
    ll h,w,k;
    cin >> h >> w >> k;
    vector<ll>x(k),y(k),v(k);
    for (ll i = 0; i < k; i++)
    {
        cin >> x[i] >> y[i] >> v[i];
    }
    ll ans=0;
    for (ll i = 0; i < k; i++)
    {
        y[i]=w+1-y[i];
        ll dx=x[i];
        ll dy=w-y[i]+1;
        ll z=0;
        if (dx<=dy)
        {
            z=((dx)*(dx+1))/2;
        }else{
            z=dy*(dx-dy);
            z%=mod;
            z+=((dy+1)*(dy))/2;
            z%=mod;
        }
        dx--,dy=w-dy;
        if (dx<=dy)
        {
            z+=(((dx)*(dx+1))/2)%mod;
            z%=mod;
        }else{
            z+=(dy*(dx-dy))%mod;
            z%=mod;
            z+=(((dy+1)*(dy))/2)%mod;
            z%=mod;
        }
        ans+=(z*v[i])%mod;
        ans%=mod;
    }
    cout << ans << endl;
}