IF COUNTIF Unique Value + 1st duplicate

Question

I have basic question related with Excel 2016. I have a huge table which displays names, as shown here

For Column B "Helper" has been used below formula :

=IF(COUNTIF(A:A,A2)=1,"Unique","")

The formula is flagging all unique values, but I want to flag also the 1st duplicate row as well, as shown in here .

I saw that formula on topic "How to get distinct values in Excel (unique + 1st duplicate occurrences)" :

=IFERROR(INDEX($A$2:$A$10, MATCH(0, INDEX(COUNTIF($B$1:B1, $A$2:$A$10), 0, 0), 0)), "")

But the formula is using duplicating list INDEX(COUNTIF($B$1:B1, and is not useful in my scenario due the fact I have millions rows.

In additional I need one value for all unique + 1st duplicating row for latter calculations. Unfortunately we are limited to Office 2016 and UNIQUE function from Office 365 cannot be used :(

Sound quite simple, but I'm stuck from couple of hours, and any help will be much appreciated.