in b1 filled down
=IF(A1="","",IF(COUNTIF($A$1:A1,A1)=1,ROW(),""))
in c1 filled down
=IF(ROW(A1)>COUNT($B$1:$B$200),"",INDEX($A$1:$A$20,MATCH(SMALL($B$1:$B$200,ROW(A1)),$B$1:$B$200,0)))