Data Range
B
C
D
E
F
2
a
1
a
2
3

Data Range
A
1
Formula Result
2
a
3
1
4
2
5
3
6
7

Array Formula Requires CTRL+SHIFT+ENTER

A
2
=IFERROR(INDEX($B$2:$F$2,MATCH(0,COUNTIF($A$1:A1,$B$2:$F$2),0)),"")

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