import sys
sys.setrecursionlimit(1 << 25)

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

tree = defaultdict(list)

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

def dfs(node, parent, dist):
    farthest = (dist, node)
    for neighbor, weight in tree[node]:
        if neighbor != parent:
            candidate = dfs(neighbor, node, dist + weight)
            if candidate[0] > farthest[0]:
                farthest = candidate
    return farthest

_, farthest_node = dfs(1, -1, 0)

max_dist, _ = dfs(farthest_node, -1, 0)

print(max(0, max_dist))