from collections import defaultdict, deque

N = int(input())
adj = defaultdict(list)
for _ in range(N-1):
    u, v, w = map(int, input().split())
    u -= 1
    v -= 1
    adj[u].append((v, w))
    adj[v].append((u, w))


def tree_dp(v, par):
    global ans
    res = [0]
    for to, w in adj[v]:
        if to == par: continue

        d = tree_dp(to, v) + w
        if d > 0:
            res.append(d)

    res.sort()
    if len(res) > 1:
        ans = max(ans, res[-1] + res[-2])

    return res[-1]


ans = 0
tree_dp(0, -1)
print(ans)