#if defined(LOCAL) or not defined(LUOGU)
#pragma GCC optimize(3)
#pragma GCC optimize("Ofast,unroll-loops")
#endif
#include<bits/stdc++.h>
using namespace std;
struct time_helper
{
#ifdef LOCAL
    clock_t time_last;
#endif
    time_helper()
    {
#ifdef LOCAL
        time_last=clock();
#endif
    }
    void test()
    {
#ifdef LOCAL
        auto time_now=clock();
        std::cerr<<"time:"<<1.*(time_now-time_last)/CLOCKS_PER_SEC<<";all_time:"<<1.*time_now/CLOCKS_PER_SEC<<std::endl;
        time_last=time_now;
#endif
    }
    ~time_helper()
    {
        test();
    }
}time_helper;
#ifdef LOCAL
#include"dbg.h"
#else
#define dbg(...) (__VA_ARGS__)
#endif
namespace Fread{const int SIZE=1<<16;char buf[SIZE],*S,*T;inline char getchar(){if(S==T){T=(S=buf)+fread(buf,1,SIZE,stdin);if(S==T)return'\n';}return *S++;}}namespace Fwrite{const int SIZE=1<<16;char buf[SIZE],*S=buf,*T=buf+SIZE;inline void flush(){fwrite(buf,1,S-buf,stdout);S=buf;}inline void putchar(char c){*S++=c;if(S==T)flush();}struct NTR{~NTR(){flush();}}ztr;}
#define getchar Fread::getchar
#define putchar Fwrite::putchar
#define Setprecision 10
#define between '\n'
#define __int128 long long
template<typename T>struct is_char{static constexpr bool value=(std::is_same<T,char>::value||std::is_same<T,signed char>::value||std::is_same<T,unsigned char>::value);};template<typename T>struct is_integral_ex{static constexpr bool value=(std::is_integral<T>::value||std::is_same<T,__int128>::value)&&!is_char<T>::value;};template<typename T>struct is_floating_point_ex{static constexpr bool value=std::is_floating_point<T>::value||std::is_same<T,__float128>::value;};namespace Fastio{struct Reader{template<typename T>typename std::enable_if_t<std::is_class<T>::value,Reader&>operator>>(T&x){for(auto &y:x)*this>>y;return *this;}template<typename T>typename std::enable_if_t<is_integral_ex<T>::value,Reader&>operator>>(T&x){char c=getchar();short f=1;while(c<'0'||c>'9'){if(c=='-')f*=-1;c=getchar();}x=0;while(c>='0'&&c<='9'){x=(x<<1)+(x<<3)+(c^48);c=getchar();}x*=f;return *this;}template<typename T>typename std::enable_if_t<is_floating_point_ex<T>::value,Reader&>operator>>(T&x){char c=getchar();short f=1,s=0;x=0;T t=0;while((c<'0'||c>'9')&&c!='.'){if(c=='-')f*=-1;c=getchar();}while(c>='0'&&c<='9'&&c!='.')x=x*10+(c^48),c=getchar();if(c=='.')c=getchar();else return x*=f,*this;while(c>='0'&&c<='9')t=t*10+(c^48),s++,c=getchar();while(s--)t/=10.0;x=(x+t)*f;return*this;}template<typename T>typename std::enable_if_t<is_char<T>::value,Reader&>operator>>(T&c){c=getchar();while(c=='\n'||c==' '||c=='\r')c=getchar();return *this;}Reader&operator>>(char*str){int len=0;char c=getchar();while(c=='\n'||c==' '||c=='\r')c=getchar();while(c!='\n'&&c!=' '&&c!='\r')str[len++]=c,c=getchar();str[len]='\0';return*this;}Reader&operator>>(std::string&str){str.clear();char c=getchar();while(c=='\n'||c==' '||c=='\r')c=getchar();while(c!='\n'&&c!=' '&&c!='\r')str.push_back(c),c=getchar();return*this;}Reader(){}}cin;const char endl='\n';struct Writer{typedef __int128 mxdouble;template<typename T>typename std::enable_if_t<std::is_class<T>::value,Writer&>operator<<(T x){for(auto &y:x)*this<<y<<between;*this<<'\n';return *this;}template<typename T>typename std::enable_if_t<is_integral_ex<T>::value,Writer&>operator<<(T x){if(x==0)return putchar('0'),*this;if(x<0)putchar('-'),x=-x;static int sta[45];int top=0;while(x)sta[++top]=x%10,x/=10;while(top)putchar(sta[top]+'0'),--top;return*this;}template<typename T>typename std::enable_if_t<is_floating_point_ex<T>::value,Writer&>operator<<(T x){if(x<0)putchar('-'),x=-x;x+=pow(10,-Setprecision)/2;mxdouble _=x;x-=(T)_;static int sta[45];int top=0;while(_)sta[++top]=_%10,_/=10;if(!top)putchar('0');while(top)putchar(sta[top]+'0'),--top;putchar('.');for(int i=0;i<Setprecision;i++)x*=10;_=x;while(_)sta[++top]=_%10,_/=10;for(int i=0;i<Setprecision-top;i++)putchar('0');while(top)putchar(sta[top]+'0'),--top;return*this;}template<typename T>typename std::enable_if_t<is_char<T>::value,Writer&>operator<<(T c){putchar(c);return*this;}Writer&operator<<(char*str){int cur=0;while(str[cur])putchar(str[cur++]);return *this;}Writer&operator<<(const char*str){int cur=0;while(str[cur])putchar(str[cur++]);return*this;}Writer&operator<<(std::string str){int st=0,ed=str.size();while(st<ed)putchar(str[st++]);return*this;}Writer(){}}cout;}
#define cin Fastio::cin
#define cout Fastio::cout
#define endl Fastio::endl

void solve();
main()
{
#if not defined(LOCAL) and not defined(ONLINE_JUDGE)
    string A="mst";freopen((A+".in").c_str(),"r",stdin);freopen((A+".out").c_str(),"w",stdout);
#endif
    int t=1;
    // cin>>t;
    while(t--)solve();
}
constexpr int p=998244353;
int fa[21][200001];
void solve()
{
    long long n;
    int m,q;
    cin>>n>>m>>q;
    if(n<=200000)
    {
        vector<tuple<int,int,int>>ops;
        for(int x=1;x<=m;x++)
        {
            int d,w;
            cin>>d>>w;
            ops.emplace_back(w,d,0);
        }
        for(int x=1;x<=q;x++)
        {
            int u,v,w;
            cin>>u>>v>>w;
            ops.emplace_back(w,u+1,v+1);
        }
        sort(ops.begin(),ops.end());
        for(int x=0;x<=20;x++)
        for(int y=1;y<=n;y++)
        fa[x][y]=y;
        auto find=[&](int i,int x)
        {
            auto Find=[&](auto self,int i,int x)->int
            {
                return x==fa[i][x]?x:fa[i][x]=self(self,i,fa[i][x]);  
            };
            return Find(Find,i,x);
        };
        int ans=0;
        for(auto [w,u,v]:ops)
        {
            int now=0;
            auto merge=[&](auto self,int l,int r,int t)->void
            {
                int u=find(t,l),v=find(t,r);
                if(u==v)return;
                fa[t][u]=v;
                if(!t)now++;
                else self(self,l,r,t-1),self(self,l+(1<<t-1),r+(1<<t-1),t-1);
            };
            if(v)merge(merge,u,v,0);
            else
            {
                int _=__lg(n-u);
                merge(merge,1,u+1,_);
                merge(merge,n-u-(1<<_)+1,n-(1<<_)+1,_);
            }
            ans=(ans+1ll*now*w)%p;
        }
        cout<<ans<<endl;
        return;
    }
    long long nn=n;
    auto work=[&](auto self,long long n,vector<tuple<long long,long long,int>>e,vector<int>&lst)->void
    {
        sort(e.begin(),e.end(),[&](auto u,auto v){return get<1>(u)<get<1>(v);});
        reverse(e.begin(),e.end());
        while(!e.empty()&&!get<1>(e.back()))e.pop_back();
        reverse(e.begin(),e.end());
        auto me=e;
        e.clear();
        for(auto q:me)
        if(e.empty()||get<1>(e.back())!=get<1>(q))e.emplace_back(q);
        long long e0=get<1>(e[0]);
        if(e.empty()||e0>=n){nn+=n;return;}
        long long k=n;
        if(2*e0>=n)nn+=2*e0-n;
        else k=n-e0;
        lst.emplace_back(get<2>(e[0]));
        if(e.size()==1){nn+=min(e0,n-e0);return;}
        long long _=(min(k,get<1>(e[1]))-1)/e0,__=_*e0;
        n-=__;
        for(int x=1;x<e.size();x++)
        get<1>(e[x])-=__;
        self(self,n,e,lst);
    };
    vector<tuple<long long,long long,int>>ops;
    vector<int>lst;
    for(int x=1;x<=m;x++)
    {
        long long d,w;
        cin>>d>>w;
        ops.emplace_back(w,d,0);
    }
    sort(ops.begin(),ops.end());
    int ans=0;
    for(int x=0;x<m;x++)
    {
        long long lnn=nn;
        nn=0;
        get<2>(ops[x])=x;
        vector<tuple<long long,long long,int>>ve;
        for(auto q:lst)ve.emplace_back(ops[q]);
        ve.emplace_back(ops[x]);
        lst.clear();
        work(work,n,ve,lst);
        ans=(ans+(lnn-nn)%p*get<0>(ops[x]))%p;
        sort(lst.begin(),lst.end());
        lst.erase(unique(lst.begin(),lst.end()),lst.end());
    }
    cout<<ans<<endl;
}