import sys
from heapq import heappop, heappush

input = sys.stdin.buffer.readline

INF = 10 ** 18


def main():
    def dijkstra(N, G, source, target):
        dist = [INF] * N
        que = [(0, source)]
        dist[source] = 0
        while que:
            c, v = heappop(que)
            if dist[v] < c:
                continue
            for t, cost in G[v]:
                if dist[v] + cost < dist[t]:
                    dist[t] = dist[v] + cost
                    heappush(que, (dist[t], t))
        return dist[target]

    N, M, K, S, T = map(int, input().split())
    S -= 1
    T -= 1
    passages = tuple(tuple(int(x) - 1 for x in input().split()) for _ in range(M))

    node_S = (0, S)
    node_T = (N - 1, T)
    node_set = {node_S, node_T}
    for a, b, c in passages:
        node_set.add((a, b))
        node_set.add((a + 1, c))
    node_dict = {t: i for i, t in enumerate(node_set)}

    L = len(node_set)
    G = [[] for _ in range(L)]

    def add_edge(s_bldg, s_floor, t_bldg, t_floor, cost):
        s = node_dict[(s_bldg, s_floor)]
        t = node_dict[(t_bldg, t_floor)]
        G[s].append((t, cost))

    for a, b, c in passages:
        add_edge(a, b, a + 1, c, 0)

    towers = [[] for _ in range(N)]
    for a, b in node_set:
        towers[a].append(b)
    for i in range(N):
        towers[i].sort()
        for j in range(len(towers[i]) - 1):
            f1 = towers[i][j]
            f2 = towers[i][j + 1]
            assert f2 > f1
            add_edge(i, f1, i, f2, f2 - f1)
            add_edge(i, f2, i, f1, f2 - f1)

    ans = dijkstra(L, G, node_dict[node_S], node_dict[node_T])

    print(ans if ans != INF else -1)


main()