public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
for (int N = sc.nextInt(); N > 0; N = sc.nextInt()) {
int M = sc.nextInt();
int L = sc.nextInt();
boolean[][] map = new boolean[N][N];
int[][] D = new int[N][N];
int[][] E = new int[N][N];
while (M-- > 0) {
int A = sc.nextInt() - 1;
int B = sc.nextInt() - 1;
map[A][B] = map[B][A] = true;
D[A][B] = D[B][A] = sc.nextInt();
E[A][B] = E[B][A] = sc.nextInt();
}
boolean[][] visited = new boolean[N][L + 1];
Queue<Edge> q = new PriorityQueue<Edge>();
q.offer(new Edge(0, 0, L));
while (!q.isEmpty()) {
Edge e = q.poll();
if (visited[e.to][e.money]) continue;
visited[e.to][e.money] = true;
if (e.to == N - 1) {
System.out.println(e.enemy);
break;
}
for (int i = 0; i < N; i++)
if (map[e.to][i]) {
if (D[e.to][i] <= e.money) q.offer(new Edge(e.enemy, i, e.money - D[e.to][i]));
q.offer(new Edge(e.enemy + E[e.to][i], i, e.money));
}
}
}
}
public Main() {
try {
in = new BufferedReader(new InputStreamReader(System.in));
// minimum distance from D to K
int numCities = nextInt();
int tradeRoutes = nextInt();
int[][] adjacencyMatrix = new int[numCities][numCities];
int[] minDistance = new int[numCities];
Arrays.fill(minDistance, 100000000);
// Arrays.fill(adjacencyMatrix, -1);
// int [] pencilCosts = new int[
Node[] cities = new Node[numCities];
for (int x = 0; x < tradeRoutes; x++) {
int cityA = nextInt() - 1;
int cityB = nextInt() - 1;
int cost = nextInt();
if (cities[cityA] == null) cities[cityA] = new Node(cityA);
if (cities[cityB] == null) cities[cityB] = new Node(cityB);
adjacencyMatrix[cityA][cityB] = cost;
adjacencyMatrix[cityB][cityA] = cost;
// cities[cityA].routes.add(new Edge(cost, cities[cityB]));
// cities[cityB].routes.add(new Edge(cost, cities[cityA]));
}
int numStores = nextInt();
int[] pencilCosts = new int[numCities];
Arrays.fill(pencilCosts, -1);
for (int x = 0; x < numStores; x++) {
int ID = nextInt() - 1;
int cost = nextInt();
pencilCosts[ID] = cost;
}
int destination = nextInt() - 1;
// if (isGood[destination]){
// }
int minCost = 100000000;
Queue<Node> Q = new LinkedList<Node>();
// PriorityQueue<Node> Q = new PriorityQueue<Node>();
minDistance[destination] = 0;
// cities[destination].distance = 0;
Q.offer(cities[destination]);
while (!Q.isEmpty()) {
Node temp = Q.poll();
for (int x = 0; x < numCities; x++) {
if (adjacencyMatrix[temp.ID][x] != 0
&& (minDistance[x] == 100000000
|| minDistance[x] > minDistance[temp.ID] + adjacencyMatrix[temp.ID][x])) {
minDistance[x] = minDistance[temp.ID] + adjacencyMatrix[temp.ID][x];
if (pencilCosts[x] != -1 && minDistance[x] < minCost) {
// System.out.println(minCost);
minCost = Math.min(minDistance[x] + pencilCosts[x], minCost);
Q.offer(cities[x]);
} else {
if (pencilCosts[x] == -1) { // why>
Q.offer(cities[x]);
}
}
// Q.offer(temp.routes.get(x).destination);
}
}
}
for (int x = 0; x < numCities; x++) {
if (pencilCosts[x] != -1
&& pencilCosts[x] + minDistance[x] < minCost
&& minDistance[x] != 100000000) {
minCost = minDistance[x] + pencilCosts[x];
}
}
System.out.println(minCost);
} catch (IOException e) {
System.out.println("IO: General");
}
}
