for(1..<>){
	<>;
	$_=<>;
	s/^BB/AB/ ||
	s/^BAA/ABA/ ||
	s/^BAB+/$&=~y,AB,BA,r/e ||
	s/^AAA/ABA/ ||
	s/^A\KAB+/$&=~y,AB,BA,r/e ||
	s/^ABA*\KB*/$&=~y,B,A,r/e ||
	0;
	s/A+/$&=~y,A,B,r/e;
	print;
}