import heapq
INF = 10**18
def dijkstra(s, edge):
    n = len(edge)
    dist = [INF]*n
    dist[s] = 0
    edgelist = []
    heapq.heappush(edgelist,(dist[s], s))
    while edgelist:
        minedge = heapq.heappop(edgelist)
        if dist[minedge[1]] < minedge[0]:
            continue
        v = minedge[1]
        for e in edge[v]:
            if dist[e[1]] > dist[v]+e[0]:
                dist[e[1]] = dist[v]+e[0]
                heapq.heappush(edgelist,(dist[e[1]], e[1]))
    return dist

import sys
import io, os
input = io.BytesIO(os.read(0,os.fstat(0).st_size)).readline

t = int(input())
n, m = map(int, input().split())
E = []
edge = [set() for i in range(n)]
for i in range(m):
    u, v, w = map(int, input().split())
    u, v = u-1, v-1
    E.append((u, v, w))
    if t == 0:
        edge[u].add((w, v))
        edge[v].add((w, u))
    else:
        edge[u].add((w, v))

ans = INF
if t == 0:
    for u, v, w in E:
        edge[u].remove((w, v))
        edge[v].remove((w, u))
        D = dijkstra(v, edge)
        ans = min(ans, w+D[u])
        edge[u].add((w, v))
        edge[v].add((w, u))
else:
    for u, v, w in E:
        edge[u].remove((w, v))
        D = dijkstra(v, edge)
        ans = min(ans, w+D[u])
        edge[u].add((w, v))
if ans < INF:
    print(ans)
else:
    print(-1)