选择题 25.  有下面程序代码：
    Private Sub Command1_Click()
    Dim x As Integer,s As Integer
    x=1
    For k=1 To 3
    x=x+1:proc x:s=s+x
    Next k
    Print s
    End Sub
    Private Sub proc(By Val a As Integer)
    Static x As Integer
    x=x+1:a=a+x
    End Sub
    程序运行后，单击命令按钮Command1，输出结果是______。