program main
  implicit none
  integer::N,D,A,B,C,i
  read *,N,D

  B = DIM(D,N)
  if(B.eq.0) then
     A = D
     C = N-D
     do i=1,A
        write(*,'(a)',advance='no'),'A'
     end do
     do i=1,C
        write(*,'(a)',advance='no'),'C'
     end do
  else
     A = N-B
     do i=1,A
        write(*,'(a)',advance='no'),'A'
     end do
     do i=1,B
        write(*,'(a)',advance='no'),'B'
     end do
  end if
  print *,
end program main