import heapq

INF = 1 << 60

t = int(input())
n, m = map(int, input().split())
edges = []
for _ in range(m):
  u, v, w = map(int, input().split())
  edges.append((u - 1, v - 1, w))

g = [[] for _ in range(n)]
if t == 0:
  for i in range(m):
    u, v, w = edges[i]
    g[u].append((v, w, i))
    g[v].append((u, w, i))
else:
  for i in range(m):
    u, v, w = edges[i]
    g[u].append((v, w, i))

ans = INF
for i in range(m):
  dst, src, w = edges[i]
  dist = [INF for _ in range(n)]
  dist[src] = 0
  hp = [(0, src)]
  while len(hp) > 0:
    cd, cur = heapq.heappop(hp)
    if cur == dst:
      break
    if cd > dist[cur]:
      continue
    for nxt, cost, j in g[cur]:
      if j == i or dist[nxt] <= dist[cur] + cost:
        continue
      dist[nxt] = dist[cur] + cost
      heapq.heappush(hp, (dist[nxt], nxt))

  ans = min(ans, dist[dst] + w)

if ans < INF:
  print(ans)
else:
  print("-1")