'''
二分枚举可能的边长上界，所有大于上界的边构成图，判断该图是不是二分图即可
二分方式可以找出最小的上界
'''


import sys
n, m = map(int, input().split())
edges = []
for i in range(m):
    s = sys.stdin.readline()
    a, b, w = map(int, s.split())
    edges.append((a, b, w))

# 判断是否是二分图
def is_valid(e):
    link = {}
    color = {}
    for a, b in e:
        if a not in link:
            link[a] = []
        if b not in link:
            link[b] = []

        link[a].append(b)
        link[b].append(a)
        color[a] = None
        color[b] = None

    def __dfs(cur, c) -> bool:
        color[cur] = c
        for ne in link[cur]:
            if color[ne] == c:
                return False
            elif color[ne] is None:
                if not __dfs(ne, 1-c):
                    return False
        return True

    for node in link.keys():
        if color[node] is None:
            if not __dfs(node, 0):
                return False
    return True

l, r = 0, 100000
ans = -1
while l <= r:
    mid = l + (r-l) // 2

    e = []
    for a, b, w in edges:
        if w > mid:
            e.append((a, b))

    if is_valid(e):
        ans = mid
        r = mid - 1
    else:
        l = mid + 1

print(ans)