n, m, k = map(int, input().split())
dist = [float('inf')] * (n + 1)
dist[1] = 0
tot_edges = [tuple(map(int, input().split())) for _ in range(m)]
for _ in range(k):
pre_dist = list(dist)
for a, b, w in tot_edges:
dist[b] = min(dist[b], pre_dist[a] + w)
print('impossible') if dist[-1] == float('inf') else print(dist[-1])
这都行?!
tql
啊这- -