#include<iostream>
#include<vector>
using namespace std;
using ll=long long;
#define rep(i,n) for(int i=0;i<n;i++)
#define rrep(i,n) for(int i=(n)-1;i>=0;i--)
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
template<class T> bool chmax(T &a, T b){if (a < b){a = b;return true;} else return false;}
template<class T> bool chmin(T &a, T b){if (a > b){a = b;return true;} else return false;}

const ll MOD=998244353;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    ll H,W,K;
    cin>>H>>W>>K;
    ll ans=0;
    rep(i,K){
        ll x,y,v;
        cin>>x>>y>>v;
        ll cnt=0;
        if(x-(y-1)>=1){
            cnt+=(2*x-y+1)*y/2;
        }else{
            cnt+=x*(x+1)/2;
        }
        cnt%=MOD;
        if(x-(W-y)>=1){
            cnt+=(2*x-W+y)*(W-y+1)/2;
        }else{
            cnt+=x*(x+1)/2;
        }
        cnt%=MOD;
        cnt-=x;
        cnt%=MOD;
        if(cnt<0)cnt+=MOD;
        ans=(ans+cnt*v)%MOD;
    }
    cout<<ans<<"\n";
}