#include <bits/stdc++.h>
using namespace std;

struct Edge {
    int u, v;
    long long w;
    bool operator<(const Edge& other) const {
        return w < other.w;
    }
};

struct DSU {
    vector<int> parent;
    DSU(int n) {
        parent.resize(n + 1);
        for (int i = 1; i <= n; i++) parent[i] = i;
    }
    int find(int v) {
        if (v == parent[v]) return v;
        return parent[v] = find(parent[v]);
    }
    bool unite(int a, int b) {
        a = find(a); b = find(b);
        if (a == b) return false;
        parent[b] = a;
        return true;
    }
};

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int n, m, p;
    if (!(cin >> n >> m >> p)) return 0;
    DSU dsu(n);
    int components = n;
    for (int i = 0; i < m; i++) {
        int u, v;
        cin >> u >> v;
        if (dsu.unite(u, v)) {
            components--;
        }
    }
    vector<Edge> new_edges(p);
    for (int i = 0; i < p; i++) {
        cin >> new_edges[i].u >> new_edges[i].v >> new_edges[i].w;
    }
    sort(new_edges.begin(), new_edges.end());
    long long total_cost = 0;
    for (auto& e : new_edges) {
        if (components == 1) break;
        if (dsu.unite(e.u, e.v)) {
            total_cost += e.w;
            components--;
        }
    }
    if (components == 1) {
        cout << total_cost << "\n";
    } else {
        cout << -1 << "\n";
    }
    return 0;
}