#include<bits/stdc++.h>
#define ll long long
using namespace std;
typedef array<ll,2> pii;
const int MAXN=5e4+5,MOD=998244353;
ll CntScc(ll n,vector<ll>&D) {
	ll cnt=0,tg=0; 
	vector <ll> op;
	priority_queue <pii,vector<pii>,greater<pii>> q;
	for(ll d:D) q.push({d,d});
	while(q.size()) {
		ll d=q.top()[0]-tg,ov=q.top()[1]; q.pop();
		if(!d) continue;
		op.push_back(ov);
		if(n<d) break;
		ll k=q.size()?min(n,q.top()[0]-tg)/d:n/d;
		n-=k*d,tg+=k*d,q.push({d+tg,ov});
		if(n<d) cnt=(cnt+d-n)%MOD;
	}
	sort(op.begin(),op.end());
	op.erase(unique(op.begin(),op.end()),op.end());
	D.swap(op);
	return (cnt+n)%MOD;
}
vector<pii> GenScc(ll n,const vector<ll>&D,const vector<ll>&V) {
	vector <pii> scc;
	for(ll v:V) scc.push_back({v,v});
	priority_queue <ll,vector<ll>,greater<ll>> q;
	for(ll d:D) q.push(d);
	ll tg=0;
	while(q.size()) {
		ll d=q.top()-tg; q.pop();
		if(!d) continue;
		if(n<d) break;
		ll k=q.size()?min(n,q.top()-tg)/d:n/d;
		n-=k*d,tg+=k*d,q.push(d+tg);
		for(auto &v:scc) {
			if(v[0]>=n+k*d) continue;
			v[0]-=d*max(0ll,k-(n+k*d-v[0]-1)/d-1);
			if(v[0]>=n&&v[0]>=d) v[0]-=d;
		}
	}
	sort(scc.begin(),scc.end());
	return scc;
}
ll n,ans=0; int m,q;
vector <array<ll,2>> F;
vector <array<ll,3>> G;
vector <ll> D[MAXN];
void solve(int l,int r,const vector<vector<ll>> &grp) {
	if(grp.empty()) return ;
	if(l==r) {
		ll w=F[l][0];
		for(auto o:grp) if(o.size()) {
			for(int i=1;i<(int)o.size();++i) {
				G.push_back({w,o[0],o[i]}),ans=(ans-w)%MOD;
			}
		}
		if(ans<0) ans+=MOD;
		return ;
	}
	int mid=(l+r)>>1;
	vector <vector<ll>> gl,gr;
	for(auto o:grp) if(o.size()>=2) {
		auto scc=GenScc(n,D[mid],o);
		sort(scc.begin(),scc.end());
		gr.push_back({});
		for(int i=0,j;i<(int)scc.size();i=j) {
			gl.push_back({});
			gr.back().push_back(scc[i][1]);
			for(j=i;j<(int)scc.size()&&scc[i][0]==scc[j][0];++j) {
				gl.back().push_back(scc[j][1]);
			}
		}
	}
	solve(l,mid,gl),solve(mid+1,r,gr);
}
int dsu[MAXN<<1];
int find(int x) { return dsu[x]^x?dsu[x]=find(dsu[x]):x; }
signed main() {
	ios::sync_with_stdio(false);
	cin>>n>>m>>q;
	F.resize(m);
	for(auto &e:F) cin>>e[1]>>e[0];
	sort(F.begin(),F.end());
	for(int i=0,lst=n%MOD;i<m;++i) {
		ll d=F[i][1],w=F[i][0];
		if(i>0) D[i]=D[i-1];
		D[i].push_back(d);
		ll cur=CntScc(n,D[i]);
		ans=(ans+w*(lst+MOD-cur))%MOD;
		lst=cur;
	}
	G.resize(q);
	vector <ll> idx;
	for(auto &e:G) {
		cin>>e[1]>>e[2]>>e[0];
		idx.push_back(e[1]);
		idx.push_back(e[2]);
	}
	sort(idx.begin(),idx.end());
	idx.erase(unique(idx.begin(),idx.end()),idx.end());
	if(m) {
		auto scc=GenScc(n,D[m-1],idx);
		vector <vector<ll>> grp;
		for(int i=0,j;i<(int)scc.size();i=j) {
			grp.push_back({});
			for(j=i;j<(int)scc.size()&&scc[i][0]==scc[j][0];++j) {
				grp.back().push_back(scc[j][1]);
			}
		}
		solve(0,m-1,grp);
	}
	int tot=idx.size();
	iota(dsu+1,dsu+tot+1,1);
	sort(G.begin(),G.end());
	for(auto e:G) {
		int u=lower_bound(idx.begin(),idx.end(),e[1])-idx.begin()+1;
		int v=lower_bound(idx.begin(),idx.end(),e[2])-idx.begin()+1;
		if(find(u)!=find(v)) ans=(ans+e[0])%MOD,dsu[find(u)]=find(v);
	}
	cout<<ans<<"\n";
	return 0;
}