#include <bits/stdc++.h>
using namespace std;
template <class T>
inline void read(T& s) {
  s = 0;
  int f = 0;
  char c = getchar();
  while ('0' > c || c > '9') f |= c == '-', c = getchar();
  while ('0' <= c && c <= '9') s = s * 10 + c - 48, c = getchar();
  s = f ? -s : s;
}
const int _ = 5e5 + 5, __ = 1e6 + 5, INF = 2e9;
int tot, head[_], nxt[_ << 1], ver[_ << 1], w[_ << 1];
inline void Add_edge(int u, int v, int d) {
  nxt[++tot] = head[u], head[u] = tot, ver[tot] = v, w[tot] = d;
}
int n, k, m, tag[_], Fa[_], X[__], Y[__], V[__], vis[__];
int dep[_], siz[_], son[_], fa[_], top[_], rev[_], dfn[_], mn[_ << 2];
inline int Find(int x) { return Fa[x] == x ? x : Fa[x] = Find(Fa[x]); }
inline void merge(int x, int y) { Fa[Find(x)] = Find(y); }
inline int lc(int p) { return p << 1; }
inline int rc(int p) { return p << 1 | 1; }
inline void f(int p, int v) { mn[p] = min(mn[p], v); }
inline void pushdown(int p) { f(lc(p), mn[p]), f(rc(p), mn[p]), mn[p] = INF; }
inline void build(int p = 1, int l = 1, int r = n) {
  mn[p] = INF;
  if (l == r) {
    mn[p] = tag[rev[l]];
    return;
  }
  int mid = (l + r) >> 1;
  build(lc(p), l, mid), build(rc(p), mid + 1, r);
}
inline void update(int ql, int qr, int v, int p = 1, int l = 1, int r = n) {
  if (ql <= l && r <= qr) return f(p, v);
  int mid = (l + r) >> 1;
  pushdown(p);
  if (ql <= mid) update(ql, qr, v, lc(p), l, mid);
  if (qr > mid) update(ql, qr, v, rc(p), mid + 1, r);
}
inline int query(int id, int p = 1, int l = 1, int r = n) {
  if (l == r) return mn[p];
  int mid = (l + r) >> 1, res;
  pushdown(p);
  if (id <= mid)
    res = query(id, lc(p), l, mid);
  else
    res = query(id, rc(p), mid + 1, r);
  return res;
}
inline void dfs(int u, int f) {
  dep[u] = dep[f] + 1, siz[u] = 1, fa[u] = f;
  for (register int i = head[u]; i; i = nxt[i]) {
    int v = ver[i];
    if (v == f) continue;
    tag[v] = w[i];
    dfs(v, u), siz[u] += siz[v];
    if (siz[son[u]] < siz[v]) son[u] = v;
  }
}
inline void dfs(int u, int f, int topf) {
  top[rev[dfn[u] = ++dfn[0]] = u] = topf;
  if (son[u]) dfs(son[u], u, topf);
  for (register int i = head[u]; i; i = nxt[i]) {
    int v = ver[i];
    if (v == f || v == son[u]) continue;
    dfs(v, u, v);
  }
}
inline void uptChain(int x, int y, int v) {
  int fx = top[x], fy = top[y];
  while (fx != fy) {
    if (dep[fx] < dep[fy]) swap(x, y), swap(fx, fy);
    update(dfn[fx], dfn[x], v), x = fa[fx], fx = top[x];
  }
  if (dep[x] > dep[y]) swap(x, y);
  update(dfn[x] + 1, dfn[y], v);
}
int main() {
  read(n), read(k), read(m);
  for (register int i = 1; i <= n; ++i) Fa[i] = i;
  for (register int u, v, i = 1; i <= k; ++i)
    read(u), read(v), merge(u, v), Add_edge(u, v, INF), Add_edge(v, u, INF);
  for (register int i = 1; i <= m; ++i) {
    read(X[i]), read(Y[i]), read(V[i]);
    if (Find(X[i]) != Find(Y[i])) {
      vis[i] = 1, merge(X[i], Y[i]);
      Add_edge(X[i], Y[i], 0), Add_edge(Y[i], X[i], 0);
    }
  }
  dfs(1, 0), dfs(1, 0, 1), build();
  for (register int i = 1; i <= m; ++i)
    if (!vis[i]) uptChain(X[i], Y[i], V[i]);
  long long ans = 0;
  for (register int i = 2; i <= n; ++i) {
    int res = query(i);
    if (res == INF)
      return puts("-1"), 0;
    else
      ans += res;
  }
  printf("%lld\n", ans);
  return 0;
}
