import sys
sys.setrecursionlimit(2 * 10 ** 5 + 10)
input = sys.stdin.readline

N = int(input())
from collections import defaultdict

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

max_diameter = 0

def dfs(u, parent):
    global max_diameter
    top1 = 0  # 最大の枝の長さ
    top2 = 0  # 2番目に大きい枝の長さ

    for v, w in graph[u]:
        if v == parent:
            continue
        child = dfs(v, u) + w
        if child < 0:
            child = 0
        if child > top1:
            top2 = top1
            top1 = child
        elif child > top2:
            top2 = child

    # このノードを経由するパスの最大長を更新
    max_diameter = max(max_diameter, top1 + top2)
    return top1

dfs(1, -1)
print(max_diameter)