#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
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(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------

int H,W,K;
ll X,Y,V;
const ll mo=998244353;
void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>H>>W>>K;
	ll ret=0;
	FOR(i,K) {
		cin>>Y>>X>>V;
		X--;
		ll num=0;
		ll Y2=max(0LL,Y-X);
		ll Y3=max(0LL,Y-(W-1-X));
		num+=(Y+Y2)*(Y-Y2+1)/2;
		num+=(Y+Y3)*(Y-Y3+1)/2;
		num-=Y;
		ret+=num%mo*V%mo;
	}
	cout<<ret%mo<<endl;
	
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}