program main
  integer :: n, i, j, d
  read(*,*) n
  if(mod(n,2) == 1) then
    write(*,*) -1
    stop
  endif

  do j = 1, n
    do i = 1, n
      if(abs(i-j)<=1) then
        if(i==j) then
          if (mod(i,2) ==1) then
            write(6,'(a)',advance="no") 'a'
          else
            write(6,'(a)',advance="no") 'b'
          end if
        else if(i==j-1 .and. mod(i,2)==1) then
          write(6,'(a)',advance="no") 'a'
        else if(mod(i,2) == 0 .and. i==j+1) then
          write(6,'(a)',advance="no") 'b'
        else
          write(6,'(a)', advance="no") '.'
        end if
      else
        write(6,'(a)',advance="no") '.'
      end if
    end do
    write(6,*)
  end do
end program main