#!/usr/bin/env python3
# %%
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
from collections import defaultdict

INF = 10 ** 18

# %%
N, M, _, S, T = map(int, readline().split())
if M == 0:
    if N == 1:
        print(abs(S - T))
    else:
        print(-1)
    exit()
m = map(int, read().split())
A, B, C = zip(*zip(m, m, m))

# %%
A_to_BC = [[] for _ in range(N + 1)]
for a, b, c in zip(A, B, C):
    A_to_BC[a].append((b, c))


# %%
A_to_BC[N].append((T, T))


# %%
def to_next_building(a, before):
    event = [(b, c) for b, c in A_to_BC[a]]
    event += [(key, -value) for key, value in before.items() if value != INF]
    event += [(-INF, -INF), (INF, -INF)]
    event.sort()
    after = defaultdict(lambda: INF)
    min_const_term = INF
    for n, x in event:
        if x > 0:
            newcost = n + min_const_term
            if after[x] > newcost:
                after[x] = newcost
        else:
            const_term = -n - x
            if min_const_term > const_term:
                min_const_term = const_term

    min_const_term = INF
    for n, x in event[::-1]:
        if x > 0:
            newcost = -n + min_const_term
            if after[x] > newcost:
                after[x] = newcost
        else:
            const_term = n - x
            if min_const_term > const_term:
                min_const_term = const_term
    return after


# %%
dist = defaultdict(int)
dist[S] = 0
for a in range(1, N + 1):
    dist = to_next_building(a, dist)
answer = dist[T] if dist[T] < INF else -1
print(answer)