import heapq

INF = 1 << 60

n, m, k, s, t = map(int, input().split())
s -= 1
t -= 1

idx = {}
idx.setdefault((0, s), len(idx))
idx.setdefault((n - 1, t), len(idx))

adj = [[0, k - 1] for _ in range(n)]
adj[0].append(s)
adj[n - 1].append(t)

arcs = []
for _ in range(m):
  a, b, c = map(int, input().split())
  a -= 1
  b -= 1
  c -= 1

  idx.setdefault((a, b), len(idx))
  idx.setdefault((a + 1, c), len(idx))
  arcs.append((idx[(a, b)], idx[(a + 1, c)], 0))

  adj[a].append(b)
  adj[a + 1].append(c)

edges = []
for b in range(n):
  floors = sorted(list(set(adj[b])))
  for i in range(len(floors) - 1):
    idx.setdefault((b, floors[i]), len(idx))
    idx.setdefault((b, floors[i + 1]), len(idx))
    u = idx[(b, floors[i])]
    v = idx[(b, floors[i + 1])]
    cost = floors[i + 1] - floors[i]
    edges.append((u, v, cost))

g = [[] for _ in range(len(idx))]
for u, v, c in arcs:
  g[u].append((v, c))

for u, v, c in edges:
  g[u].append((v, c))
  g[v].append((u, c))

dist = [INF for _ in range(len(idx))]
src = idx[(0, s)]
dst = idx[(n - 1, t)]
dist[src] = 0
hp = [(dist[src], src)]
while len(hp) > 0:
  cd, cur = heapq.heappop(hp)
  if cd > dist[cur]:
    continue
  for nxt, cost in g[cur]:
    if dist[cur] + cost < dist[nxt]:
      dist[nxt] = dist[cur] + cost
      heapq.heappush(hp, (dist[nxt], nxt))

if dist[dst] < INF:
  print(dist[dst])
else:
	print("-1")