样例1：333ms，样例2：429ms，样例8TLE，其他全A 下面是我的Python代码，我感觉已经没法再优化了，求助啊！！拓扑排序的做法我已经A了，现在想研究下Dijkstra怎么A

import sys
import heapq
input = lambda: sys.stdin.readline().strip()
def Dijkstra(graph, n):
    pqueue = [(0, 1)]
    distance = {i: -float('inf') for i in graph}
    distance[1] = 0
    while pqueue:
        dist, vertex = heapq.heappop(pqueue)
        dist = -dist
        if dist < distance[vertex]:
            continue
        for node in graph[vertex]:
            Dist = dist + graph[vertex][node]
            if Dist > distance[node]:
                distance[node] = Dist
                heapq.heappush(pqueue, (-Dist, node))
    print(distance[n] if distance[n] != -float('inf') else -1)
def read(graph, vis):
    a, b, c = map(int, input().split())
    if vis[a][b] and graph[a][b] >= c:
        return
    graph[a][b] = c
    vis[a][b] = True
def solve():
    n, m = map(int, input().split())
    graph = {i: {} for i in range(1, n + 1)}
    vis = [[False for j in range(n + 1)] for i in range(n + 1)]
    for _ in range(m):
        read(graph, vis)
    Dijkstra(graph, n)
solve()