Finding only triple occurances of duplicate items

Hi, there's rows A and B as follows:

A B
1 9
6 7
21 30
1 9
9 1
21 30

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I am trying to display

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C D
1 9

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as the resolution .

By using the formula
"=IFERROR(INDEX(A$1:A$5,SMALL(IF(FREQUENCY($A$1:$A$7*$B$1:$B$7/

($A$1:$A$7+$B$1:$B$7),

$A$1:$A$7*$B$1:$B$7/($A$1:$A$7+$B$1:$B$7))>1,ROW($A$1:$A$7)-

MIN(ROW($A$1:$A$7))+1),ROWS($1:1))),"") "

the resolution is

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C D
1 9
21 30

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As there are duplicates in upper example however desired answer is supposed to be only 1 and 9 in Rows C and D excluding 21 and 30 because they have occurred only twice not thrice.

Is there a way to achieve the desired resolution by editing or entering an entirely new formula or way?

thanks

Perhaps you need helper column, and the array formula is

put in D2 and entered as array and copied down

=IFERROR(INDEX($F$2:$F$7,MATCH(0,COUNTIF(D1:$D$1,$F$2:$F$7)+IF(COUNTIF($F$2:$F$7,$F$2:$F$7)>1,0,1),0)),"")

Thank for the answer, your awesome