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 PYTHON):

Solution:
#!/usr/bin/python
# -*- coding: utf-8 -*-
import sys,collections,itertools,re,math,fractions,decimal,random,array,bisect,heapq

# decimal.getcontext().prec = 50
sys.setrecursionlimit(100000)
MOD = 10**9 + 7

def dijkstra(g, v_size, st):
    """Dijkstra method"""

    d = [float('inf')] * v_size
    d[st] = 0

    que = [(0, st)]     # (min_dist, vertex)
    heapq.heapify(que)

    while len(que) > 0:
        dist, v0 = heapq.heappop(que)
        if d[v0] < dist: continue
        for v1, dist in g[v0]:
            if d[v1] > d[v0] + dist:
                d[v1] = d[v0] + dist
                heapq.heappush(que, (d[v1], v1))

    return d

def solve(f):
    n, m = f.read_int_list()
    s, t = f.read_int_list()
    g = collections.defaultdict(list)
    for m in xrange(m):
        u, v, d = f.read_int_list()
        g[u-1].append((v-1, d))
        g[v-1].append((u-1, d))

    d = dijkstra(g, n, s-1)

    cand = []
    for i in xrange(n):
        if d[t-1] == d[i]*2: cand.append((i,i))

    memo = [0]*n
    memo[t-1] = 1
    ary = [(d[i], i) for i in xrange(n)]
    ary.sort(reverse=True)

    for _, v in ary:
        for vi, di in g[v]:
            if d[v]-di == d[vi]:
                memo[vi] = (memo[vi]+memo[v])%MOD
                if d[vi]*2 < d[t-1] < (d[vi] + di)*2:
                    cand.append((vi, v))

    memo2 = [0]*n
    memo2[s-1] = 1

    ary.sort()
    for _, v in ary:
        for vi, di in g[v]:
            if d[v]+di == d[vi]:
                memo2[vi] = (memo2[vi]+memo2[v])%MOD

    cnt = []
    for v1, v2 in cand:
        cnt.append((memo2[v1]*memo[v2])%MOD)

    s = sum(cnt)
    ans = 0
    for ci in cnt:
        ans = (ans+ci*(s-ci))%MOD

    return ans


class Reader(object):
    def __init__(self, filename=None):
        self.file = open(filename) if filename is not None else None
        self.case = 1

    def __readline(self):
        return self.file.next().strip() if self.file else raw_input()

    def next_case(self):
        self.file.next()
        self.case += 1

    def read_int(self): return int(self.__readline())
    def read_float(self): return float(self.__readline())
    def read_long(self): return long(self.__readline())
    def read_decimal(self): return decimal.Decimal(self.__readline())
    def read_str(self): return self.__readline()

    def read_int_list(self): return map(int, self.__readline().split())
    def read_float_list(self): return map(float, self.__readline().split())
    def read_long_list(self): return map(long, self.__readline().split())
    def read_decimal_list(self): return map(decimal.Decimal, self.__readline().split())
    def read_str_list(self): return self.__readline().split()

if __name__ == '__main__':
    filename = sys.argv[1] if len(sys.argv) > 1 else None
    f = Reader(filename)
    if f.file:
        while True:
            print "Case #%d\n"%f.case, solve(f)
            try:
                f.next_case()
            except StopIteration:
                break
    else:
        print solve(f)