import sys
from heapq import heappush, heappop
def dijkstra(s):
dist = [float('inf')] * (N + 1)
dist[s] = 0
priority_queue = [(0, s)]
while priority_queue:
w1, u = heappop(priority_queue)
if dist[u] < w1:
continue
for w2, v in graph[u]:
w = w1 + w2
if w < dist[v]:
dist[v] = w
heappush(priority_queue, (w, v))
return dist
input = sys.stdin.readline
N, E = map(int, input().split())
graph = [[] for _ in range(N + 1)]
for _ in range(E):
A, B, C = map(int, input().split())
graph[A].append((C, B))
graph[B].append((C, A))
V1, V2 = map(int, input().split())
path1 = [(1, V1), (V1, V2), (V2, N)]
path2 = [(1, V2), (V2, V1), (V1, N)]
count1 = 0
count2 = 0
for i in range(3):
s1, e1 = path1[i]
s2, e2 = path2[i]
count1 += dijkstra(s1)[e1]
count2 += dijkstra(s2)[e2]
count = min(count1, count2)
if count == float('inf'):
print(-1)
else:
print(count)
