n, m = map(int, input().split())
adj = [[] for _ in range(n)]
for _ in range(m):
    raw = input().split()
    u, v = map(int, raw[:2])
    d = float(raw[-1])
    adj[u].append([v, d])
s, f = map(int, input().split())

visited = [False] * n
pre = [None] * n
post = [None] * n
clock = 0


def dfs(u):
    global clock
    pre[u] = clock
    clock += 1
    visited[u] = True
    for v, _ in adj[u]:
        if not visited[v]:
            dfs(v)
    post[u] = clock
    clock += 1


for u in range(n):
    if not visited[u]:
        dfs(u)

l = [[post[u], u] for u in range(n)]
l.sort()
dist = [float("+inf")] * n
dist[s] = 0

for _, u in reversed(l):
    for v, d in adj[u]:
        dist[v] = min(dist[v], dist[u] + d)
print(dist[f])