Problem: We have a graph with N vertices and M edges, and there are two people on the graph: Takahashi and Aoki.

The i-th edge connects Vertex U_i and Vertex V_i. The time it takes to traverse this edge is D_i minutes, regardless of direction and who traverses the edge (Takahashi or Aoki).

Takahashi departs Vertex S and Aoki departs Vertex T at the same time. Takahashi travels to Vertex T and Aoki travels to Vertex S, both in the shortest time possible. Find the number of the pairs of ways for Takahashi and Aoki to choose their shortest paths such that they never meet (at a vertex or on an edge) during the travel, modulo 10^9 + 7.

Constraints

* 1 \leq N \leq 100 000
* 1 \leq M \leq 200 000
* 1 \leq S, T \leq N
* S \neq T
* 1 \leq U_i, V_i \leq N (1 \leq i \leq M)
* 1 \leq D_i \leq 10^9 (1 \leq i \leq M)
* If i \neq j, then (U_i, V_i) \neq (U_j, V_j) and (U_i, V_i) \neq (V_j, U_j).
* U_i \neq V_i (1 \leq i \leq M)
* D_i are integers.
* The given graph is connected.

Input

Input is given from Standard Input in the following format:


N M
S T
U_1 V_1 D_1
U_2 V_2 D_2
:
U_M V_M D_M


Output

Print the answer.

Examples

Input

4 4
1 3
1 2 1
2 3 1
3 4 1
4 1 1


Output

2


Input

3 3
1 3
1 2 1
2 3 1
3 1 2


Output

2


Input

8 13
4 2
7 3 9
6 2 3
1 6 4
7 6 9
3 8 9
1 2 2
2 8 12
8 6 9
2 5 5
4 2 18
5 3 7
5 1 515371567
4 8 6


Output

6

Solution (in JAVA):

Solution:
import java.util.*;
import java.io.*;

public class Main {

	class Edge {
		int to, cost;

		public Edge(int to, int cost) {
			super();
			this.to = to;
			this.cost = cost;
		}

	}

	int mod = 1000000007;

	List<Edge>[] graph;

	long[] distS, countS, distT, countT;

	class Vertex implements Comparable<Vertex> {
		int id;
		long dist;

		public Vertex(int id, long dist) {
			super();
			this.id = id;
			this.dist = dist;
		}

		@Override
		public int compareTo(Vertex o) {
			if (dist != o.dist) {
				return Long.compare(dist, o.dist);
			}
			return id - o.id;
		}
	}

	void calc(long[] dist, long[] count, int s) {
		long INF = Long.MAX_VALUE / 3;
		Arrays.fill(dist, INF);
		dist[s] = 0;
		TreeSet<Vertex> q = new TreeSet<>();
		q.add(new Vertex(s, dist[s]));
		count[s] = 1;
		while (!q.isEmpty()) {
			Vertex cur = q.pollFirst();
			for (int t = 0; t < graph[cur.id].size(); t++) {
				Edge e = graph[cur.id].get(t);
				if (cur.dist + e.cost < dist[e.to]) {
					Vertex v = new Vertex(e.to, dist[e.to]);
					q.remove(v);
					v.dist = dist[e.to] = cur.dist + e.cost;
					count[e.to] = count[cur.id];
					q.add(v);
				} else if (cur.dist + e.cost == dist[e.to]) {
					count[e.to] += count[cur.id];
					if (count[e.to] >= mod) {
						count[e.to] -= mod;
					}
				}
			}
		}
	}

	void solve() {
		int n = in.nextInt(), m = in.nextInt();
		graph = new List[n];
		int s = in.nextInt() - 1, t = in.nextInt() - 1;

		for (int i = 0; i < n; i++) {
			graph[i] = new ArrayList<>();
		}
		for (int i = 0; i < m; i++) {
			int from = in.nextInt() - 1, to = in.nextInt() - 1, cost = in.nextInt();
			graph[from].add(new Edge(to, cost));
			graph[to].add(new Edge(from, cost));
		}

		distS = new long[n];
		distT = new long[n];
		countS = new long[n];
		countT = new long[n];
		calc(distS, countS, s);
		calc(distT, countT, t);

		long result = countS[t] * countS[t] % mod;
		long distST = distT[s];
		if (distST % 2 == 0) {
			for (int i = 0; i < n; i++) {
				if (distS[i] + distT[i] == distST && distS[i] * 2 == distST) {
					result -= countS[i] * countS[i] % mod * countT[i] % mod * countT[i] % mod;
					if (result < 0) {
						result += mod;
					}
				}
			}
		}

		for (int i = 0; i < n; i++) {
			for (Edge e : graph[i]) {
				int from = i, to = e.to;
				if (distS[from] + e.cost + distT[to] == distST && 2 * distS[from] < distST && 2 * distT[to] < distST) {
					result -= countS[from] * countS[from] % mod * countT[to] % mod * countT[to] % mod;
					if (result < 0) {
						result += mod;
					}
				}
			}
		}

		out.println(result);
	}

	FastScanner in;
	PrintWriter out;

	void run() {
		in = new FastScanner();
		out = new PrintWriter(System.out);
		solve();
		out.close();
	}

	class FastScanner {
		BufferedReader br;
		StringTokenizer st;

		public FastScanner() {
			br = new BufferedReader(new InputStreamReader(System.in));
		}

		public FastScanner(String s) {
			try {
				br = new BufferedReader(new FileReader(s));
			} catch (FileNotFoundException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}

		public String nextToken() {
			while (st == null || !st.hasMoreTokens()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
				}
			}
			return st.nextToken();
		}

		public int nextInt() {
			return Integer.parseInt(nextToken());
		}

		public long nextLong() {
			return Long.parseLong(nextToken());
		}

		public double nextDouble() {
			return Double.parseDouble(nextToken());
		}
	}

	public static void main(String[] args) {
		new Main().run();
	}
}