def solve():
    import sys
    sys.setrecursionlimit(1 << 25)
    N = int(sys.stdin.readline())
    from collections import defaultdict

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

    ans = 0

    def dfs(u, parent):
        nonlocal ans
        max1, max2 = 0, 0  # 部分木の最大・2番目
        for v, w in graph[u]:
            if v == parent: continue
            res = dfs(v, u) + w
            res = max(res, 0)  # 負なら通らない
            if res > max1:
                max1, max2 = res, max1
            elif res > max2:
                max2 = res
        ans = max(ans, max1 + max2)
        return max1

    dfs(0, -1)
    print(ans)
solve()