import java.util.*;
public class RunAStar {
    static boolean flag=true;
    static NodeGeo[] nodes;
    static int src;
    static int dst;
    public static void main(String[] args) {
	for (int i=0; i<args.length; i++) {
	    if (args[i].equals("-n")) flag=false;
	}
	doInput();
	PFSearch dj = new PFSearch(nodes);
	if (flag) NodeGeo.dst = nodes[dst]; // if (flag==true) A*, else PFS
	dj.solve(nodes[src],nodes[dst]);
	double len = nodes[dst].value;
	System.out.println((len==Double.MAX_VALUE) ? -1 : len);
    }
    static void doInput() {
	Scanner sc = new Scanner(System.in);
	int nTown = sc.nextInt(); // 都市の数
	nodes = new NodeGeo[nTown];
	for (int i=0; i<nTown; i++) {
	    nodes[i] = new NodeGeo(sc.nextInt(),sc.nextDouble(),sc.nextDouble());
	}
	int nRoute = sc.nextInt(); // 道路の数
	for (int i=0; i<nRoute; i++) {
	    int from = sc.nextInt();
	    int to = sc.nextInt();
	    double len = sc.nextDouble();
	    nodes[from].edges.add(new Edge(nodes[from],nodes[to],len));
	    nodes[to].edges.add(new Edge(nodes[to],nodes[from],len));
	}
	src = sc.nextInt();	// 始点
	dst = sc.nextInt();	// 目的地
    }
}