from collections import defaultdict
from heapq import heappush, heappop

INF = 1 << 60
T = int(input())
N, M = map(int, input().split())

adj = defaultdict(list)
for _ in range(M):
    U, V, W = map(int, input().split())
    U -= 1
    V -= 1
    adj[U].append((V, W))
    if T == 0:
        adj[V].append((U, W))


def solve():
    res = INF

    for s in range(N):
        for t, tw in adj[s]:
            # 辺 (s, t) を除外し、t から s への最短距離を求める
            dists = [INF] * N
            dists[t] = 0
            q = [(0, t)]
            while q:
                d, v = heappop(q)
                if dists[v] != d: continue

                for to, w in adj[v]:
                    if (v, to) == (t, s): continue

                    nd = dists[v] + w
                    if dists[to] > nd:
                        dists[to] = nd
                        heappush(q, (nd, to))

            res = min(res, dists[s] + tw)

    if res == INF:
        return -1
    return res


ans = solve()
print(ans)