import sys
import heapq
input = sys.stdin.buffer.readline
sys.setrecursionlimit(10 ** 7)
inf = 10**18

T = int(input())
N, M = map(int, input().split())
edge = []
G = [[] for _ in range(N)]
for i in range(M):
    a, b, c = map(int, input().split())
    a -= 1
    b -= 1
    edge.append((a, b, c))
    G[a].append((b, c))
    if T == 0:
        G[b].append((a, c))


def dijkstra(i):
    s, t, c = edge[i]
    dist = [inf] * N
    dist[t] = 0
    que = [(0, t)]
    while que:
        dv, v = heapq.heappop(que)
        if dist[v] < dv:
            continue
        if v == s:
            break
        for u, du in G[v]:
            if (v, u) in ((s, t), (t, s)):
                continue
            if dist[u] > dv + du:
                dist[u] = dv + du
                heapq.heappush(que, (dv + du, u))
    return c + dist[s]


ans = inf
for i in range(M):
    d = dijkstra(i)
    if d < ans:
        ans = d
if ans >= inf:
    ans = -1
print(ans)