如下程序是从键盘上输入一个正整数，找出大于或等于该数的第一个素数。请完善程序。
Private Sub command1_Click()        
Dim i As Integer, x As Integer, y As Integer, flag As Boolean     
flag = False         
x = InputBox("请输入一个正整数", "输入正整数")        
y = x         
Do While Not flag          
i = 2          
      flag =________________
Do While flag And i <= x / 2              
If x Mod i = 0 Then                  
flag = False             
        Else                           ________________
End If         
Loop          
If Not flag Then  x=x+1        
Loop        
Print "大于或等于" & Str(y) & "的第一个素数是：" & Str(x)
End Sub