import sys
input = sys.stdin.readline

def main():
    N = int(input())
    adj = [[] for _ in range(N)]
    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))

    parent = [-1] * N
    order = []
    stack = [0]
    parent[0] = -2  # ルートの親を特別マーク
    while stack:
        u = stack.pop()
        order.append(u)
        for v, _ in adj[u]:
            if parent[v] == -1:
                parent[v] = u
                stack.append(v)

    down = [0] * N
    NEG_INF = float('-inf')
    ans = NEG_INF

    # 逆順に DP
    for u in reversed(order):
        best1 = NEG_INF
        best2 = NEG_INF
        for v, w in adj[u]:
            if parent[v] == u:
                dc = down[v] + w
                if dc >= best1:
                    best2 = best1
                    best1 = dc
                elif dc > best2:
                    best2 = dc

        if best1 != NEG_INF:
            down[u] = best1
            ans = max(ans, best1)
        if best2 != NEG_INF:
            ans = max(ans, best1 + best2)

    print(ans)

if __name__ == '__main__':
    main()