import sys
input = sys.stdin.readline
from collections import defaultdict
from heapq import *

def dijkstra(s, t):
    dist = [10**18]*c
    dist[s] = 0
    pq = []
    heappush(pq, (dist[s], s))
    
    while pq:
        d, v = heappop(pq)
        
        if dist[v]<d:
            continue
        
        for nv, w in adj_list[v]:
            if dist[nv]>dist[v]+w:
                dist[nv] = dist[v]+w
                heappush(pq, (dist[nv], nv))
    
    return dist[t]

N, M, K, S, T = map(int, input().split())
node = [set() for _ in range(N)]
node[0].add(S)
node[-1].add(T)
abc = [tuple(map(int, input().split())) for _ in range(M)]

for ai, bi, ci in abc:
    node[ai-1].add(bi)
    node[ai].add(ci)

serial = defaultdict(dict)
c = 0

for i in range(N):
    l = list(node[i])
    l.sort()
    
    for j in range(len(l)):
        serial[i][l[j]] = c
        c += 1

adj_list = [[] for _ in range(c)]

for i in range(N):
    l = list(serial[i].items())
    
    for j in range(len(l)-1):
        ps, s = l[j]
        pt, t = l[j+1]
        adj_list[s].append((t, pt-ps))
        adj_list[t].append((s, pt-ps))

for ai, bi, ci in abc:
    s = serial[ai-1][bi]
    t = serial[ai][ci]
    adj_list[s].append((t, 0))

ans = dijkstra(serial[0][S], serial[N-1][T])

if ans==10**18:
    print(-1)
else:
    print(ans)