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))

max_path = 0

def dfs(node, parent):
    global max_path
    best1, best2 = 0, 0  

    for neighbor, weight in tree[node]:
        if neighbor == parent:
            continue
        gain = dfs(neighbor, node) + weight
        gain = max(0, gain)  
        if gain > best1:
            best1, best2 = gain, best1
        elif gain > best2:
            best2 = gain

    max_path = max(max_path, best1 + best2)
    return best1

dfs(1, -1)
print(max_path)