星期天，小龙来到动物园游玩，园内共有N个景点（可在10个以上），每个景点都有一个标号，标号为1至N。现在只知道每个景点有一条路连接下一个景点。小龙想知道，根据这些道路信息，从其中一个景点出发，最后再回到出发景点，最多能游玩多少个景点。

例如，共有N=5个景点，每个景点连接的下一个景点分别是2，4，5，5，2。

景点号	1	2	3	4	5
下一景点号	2	4	5	5	2

则他可以从2号景点出发，最多可以游玩2号、4号、5号三个景点。

程序代码如下：

Private Sub Command1_Click()Dim a(1 To 100) As Integer, d(1 To 100) As Integer

    Dim jd As String, m As String, c As Integer, i As Integer

    Dim s As Integer, p As Integer, k As Integer, ans As Integer

    jd = Text1.Text + ","

    s = 0: c = 0

    For i = 1 To Len(jd)

        m = Mid(jd, i, 1)

        If m <> "," Then

               ①   

        Else

            c = c + 1: a(c) = s: s = 0

        End If

    Next i

    ans = 0: k = 0

    For i = 1 To c

        For k = 1 To c

            d(k) = 0

        Next k

        If d(i) = 0 Then

            p = i

            Do While p <= c

                If d(p) = 0 Then

                    k = k + 1: d(p) = k

                Else

                                  

                If y > ans Then ans = y

                    k = 0

                    Exit Do

                End If

               

            Loop

        End If

    Next i

    Text2.Text = Str(ans)

End Sub