#include <algorithm>
#include <bitset>
#include <cstdint>
#include <iostream>
#include <numeric>
#include <vector>
#include <utility>
using namespace std;

const int N = 2e5 + 8;
const int p = 998244353;
int64_t n, m, q;
vector<pair<int64_t, int64_t> > gg[N];
vector<pair<int64_t, pair<int64_t, int64_t> > > vec;

int fa[N], siz[N];
inline void init(int n) {
  iota(fa, fa + n + 1, 0), fill(siz, siz + n + 1, 1);
}
int ask(int x) {
  return fa[x] == x? x: fa[x] = ask(fa[x]);
}
void merge(int x, int y) {
  int a = ask(x), b = ask(y);
  if (a == b) return ;
  if (siz[a] > siz[b]) swap(a, b);
  fa[a] = b;
  siz[b] += siz[a];
}

bitset<N> vis;
void dfs(int x) {
  if (vis[x]) return ;
  vis[x] = true;
  for (auto p: gg[x])
    dfs(p.first);
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0), cout.tie(0);
  cin >> n >> m >> q;
  for (int i = 0; i < m; ++i) {
    int64_t d, x;
    cin >> d >> x;
    for (int j = 0; j + d < n; ++j) {
      vec.push_back(make_pair(x, make_pair(j, j + d)));
      gg[j].push_back(make_pair(j + d, x));
      gg[j + d].push_back(make_pair(j, x));
    }
  }
  for (int i = 0; i < q; ++i) {
    int64_t u, v, w;
    cin >> u >> v >> w;
    vec.push_back(make_pair(w, make_pair(u, v)));
    gg[u].push_back(make_pair(v, w));
    gg[v].push_back(make_pair(u, w));
  }
  int64_t kk = 0;
  for (int i = 0; i < n; ++i) {
    if (!vis[i]) ++kk;
    dfs(i);
  }
  clog << kk << endl;
  sort(vec.begin(), vec.end());
  kk = n - kk;
  int64_t tt = 0, sum = 0;
  init(n);
  for (auto e: vec) {
    if (ask(e.second.first) == ask(e.second.second)) continue;
    merge(e.second.first, e.second.second);
    sum += e.first;
    if (sum >= p) sum -= p;
    ++tt;
    if (tt == kk) break;
  }
  cout << sum << '\n';
  return 0;
}