from collections import deque
from heapq import heappop, heappush
from typing import List, Tuple

INF = int(1e18)


def minCostCycle(n: int, edges: List[Tuple[int, int, int]], directed: bool) -> int:
    """O(V*(V+E)*logV)求最小环权值之和,不存在返回INF."""
    res = INF
    maxWeight = max(w for *_, w in edges)
    res = INF
    for i, e1 in enumerate(edges):
        from_, to, weight = e1
        adjList = [[] for _ in range(n)]
        for j, e2 in enumerate(edges):
            if i != j:
                u, v, w = e2
                adjList[u].append((v, w))
                if not directed:
                    adjList[v].append((u, w))
        cand = _bfs01(adjList, from_, to) if maxWeight <= 1 else _dijkstra(adjList, from_, to)
        res = min(res, weight + cand)
    return res


def _bfs01(adjList: List[List[Tuple[int, int]]], start: int, target: int) -> int:
    n = len(adjList)
    dist = [INF] * n
    dist[start] = 0
    queue = deque([start])
    while queue:
        cur = queue.popleft()
        if cur == target:
            return dist[cur]
        for next, weight in adjList[cur]:
            cand = dist[cur] + weight
            if cand < dist[next]:
                dist[next] = cand
                if weight == 0:
                    queue.appendleft(next)
                else:
                    queue.append(next)
    return INF


def _dijkstra(adjList: List[List[Tuple[int, int]]], start: int, target: int) -> int:
    n = len(adjList)
    dist = [INF] * n
    dist[start] = 0
    pq = [(0, start)]
    while pq:
        curDist, cur = heappop(pq)
        if cur == target:
            return curDist
        if dist[cur] < curDist:
            continue
        for next, weight in adjList[cur]:
            cand = curDist + weight
            if cand < dist[next]:
                dist[next] = cand
                heappush(pq, (cand, next))
    return INF


if __name__ == "__main__":
    directed = int(input())
    n, m = map(int, input().split())
    edges = []
    for _ in range(m):
        u, v, w = map(int, input().split())
        u -= 1
        v -= 1
        edges.append((u, v, w))
    res = minCostCycle(n, edges, directed == 1)
    if res == INF:
        res = -1
    print(res)