import numpy as np
from scipy.sparse.csgraph import dijkstra
from scipy.sparse import csr_matrix

N, M, P, Q, T = map(int, input().split())
P -= 1
Q -= 1
edges = np.array([tuple(map(int, input().split())) for _ in range(M)]).T

matr = csr_matrix((edges[2], (edges[:2] - 1)), shape=(N, N))
way_1, way_p, way_q = dijkstra(matr, indices=(0, P, Q), directed=False).astype(int)

if way_1[P] + way_1[Q] + way_p[Q] <= T:
    print(T)
    exit()

possible = ((way_1 + way_p) * 2 <= T) & ((way_1 + way_q) * 2 <= T)
if not np.any(possible):
    print(-1)
    exit()
time = T - np.maximum(way_p, way_q) * 2
print(time.max())