Ask! List grouped data with EXCEL function. Divide the number of 12 into two groups to form 1 group. Each group has 6 non-repeated complex numbers, and each group has 12 non-repeated complex numbers.

Select a range where duplicates are not allowed. For the whole worksheet, select Ctrl+A, and click (Data)-(Validity)-(Settings) in the menu (select the Custom tab in the Allow drop-down list box)-(enter = COUNTIF ($6544) in the text box under Formula). (Switch to the Error Warning tab)-(Set the style as a stop option (or set it as a warning or information as needed)-and then click the OK button.