from collections import defaultdict

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


def tree_dp(v, par):
    dp0 = 0  # 頂点 v は端点
    dp1 = 0  # 頂点 v は中継点(or 部分木のパスの最長長さ)

    for to, w in adj[v]:
        if to == par: continue

        r_dp0, r_dp1 = tree_dp(to, v)
        pp0 = pp1 = 0
        dp0, pp0 = pp0, dp0
        dp1, pp1 = pp1, dp1

        dp0 = max(pp0, r_dp0 + w)
        dp1 = max(pp1,
                  r_dp1,  # 部分木の最長長さ
                  pp0 + r_dp0 + w)  # 頂点 v は中継点

    return dp0, dp1


dp0, dp1 = tree_dp(0, -1)
ans = max(dp0, dp1)
print(ans)