Extracting Column heading from Table

I have a table with column headings and under each column is the data. Given the inputs, I want to create a formula to achieve the desired result highlighted in Yellow.

I know this must be fairly simple but given my limited knowledge, any help would be greatly appreciated! I am using a desktop version of MS Excel 2013



Excel.xlsx

B8=IFERROR(INDEX($A$1:$C$1,,AGGREGATE(15,6,COLUMN($A$1:$C$1)-COLUMN($A$1)+1/($A$2:$C$4=$A8),COLUMNS($A$1:A1))),"")

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Thank you, this works on my desktop MS Excel. I'm trying to upload this to my Google Sheets for sharing and it seems like it doesn't like the Aggregate formula. Would it be possible to help me break it down to a Google Sheets friendly formula

If you are going to use google sheets, you should have mentioned in the OP.

B8
=INDEX($A$1:$C$1,,SUMPRODUCT(($A$2:$C$4=A8)*COLUMN($A$2:$C$4)))

copied down.