若有一个三位数满足：x=a³+b³+c³（其中a、b、c分别是该三位数的个位、十位和百位数字），则称该三位数为水仙花数。完成程序填空实现输入数的水仙数判断。
Dim a As Double, b As Double, c As Double, x As Double
x = Val(InputBox("输入一个数据x"))
If  ①______________________ Then
a = x mod 10
b = ②_________________________
c = x \ 100
If  ③__________________________ Then
Print "是水仙花数！"
Else
Print "不是水仙花数！"
  ④_____________________________________
  ⑤_____________________________________
Print "请输入三位数！"
End If