#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=(a);i<(b);i++)
const int maxn=5e5+5;
int n,k,m,u,v,w,f[maxn],d[maxn]; array<int,2> p[maxn]; vector<array<int,2> > ady[maxn]; vector<array<int,3> > e; long long cst;
int find(int x) {return f[x]==x?x:f[x]=find(f[x]); }
void dfs(int x) {
	for(auto [y,w]:ady[x]) if(y!=p[x][0]) {
		p[y]={x,w}; d[y]=d[x]+1;
		dfs(y);
	}
}
void ae(int x, int y, int w) {
	ady[x].push_back({y,w});
	ady[y].push_back({x,w});
}
int main(){
    ios_base::sync_with_stdio(0);
	cin>>n>>k>>m;
	rep(i,1,n+1) f[i]=i;
	rep(i,0,k) {
		cin>>u>>v;
		ae(u,v,0);
		f[find(u)]=find(v);
	}
	rep(i,0,m) {
		cin>>u>>v>>w;
		if(find(u)!=find(v)) f[f[u]]=f[v], ae(u,v,w);
		else e.push_back({u,v,w});
	}
	dfs(1);
	rep(i,1,n+1) f[i]=i;
	for(auto [u,v,w]: e) {
		u=find(u),v=find(v);
		while(u!=v) {
			if(d[u]<d[v]) swap(u,v);
			auto [pu,w2] = p[u];
			if(!w2) cst+=w, k--;
			u=f[u]=find(pu);
		}
	}
	cout<<(k?-1:cst)<<"\n";
}