Hi to all!
Another options (No CSE):
=AGGREGATE(15,6,(ROW($B$2:$B$9)-1)/(C2&D2=$A$2:$A$9&$B$2:$B$9),1)
=SUMPRODUCT(--(C2&D2=$A$2:$A$9&$B$2:$B$9),ROW($B$2:$B$9)-1)
=LOOKUP(2,1/(C2&D2=$A$2:$A$9&$B$2:$B$9),ROW($B$2:$B$9)-1)
=MATCH(C2&D2,INDEX($A$2:$A$9&$B$2:$B$9,),)
Blessings!