import sys
sys.setrecursionlimit(1 << 25)

N = int(input())
graph = [[] for _ in range(N)]

for _ in range(N - 1):
    u, v, w = map(int, input().split())
    u -= 1  # 0-indexed
    v -= 1
    graph[u].append((v, w))
    graph[v].append((u, w))

max_diameter = 0

def dfs(v, parent):
    global max_diameter
    longest = 0  # v から最長の子への距離
    second_longest = 0  # 2番目に長い子

    for child, weight in graph[v]:
        if child == parent:
            continue
        d = dfs(child, v) + weight
        if d > longest:
            second_longest = longest
            longest = d
        elif d > second_longest:
            second_longest = d

    # 直径候補の更新
    max_diameter = max(max_diameter, longest + second_longest)
    return longest

dfs(0, -1)
print(max_diameter)