Here are some keywords related to user questions:

['device operating system description', "device's NT domain", 'destination NT domain', 'source host port', 'number of bytes for the event response body', 'attacker host MAC address', 'device time zone offset from UTC', 'UTC time zone', 'attacker region name', 'list of basic event IDs associated with the event', 'connector time zone', 'source process ID', 'source DNS domain', 'device domain', 'device vendor', 'event type', 'event result type', 'technical type of subject behavior', 'event attack source is source or destination', 'source Windows NT domain', 'source host name', 'device-defined event classification ID', 'source process name', 'target region code', 'device software version', 'event session ID', 'source fully qualified domain name', 'Uniform Resource Locator', 'part of URL representing the request content', 'device product name', 'object behavior type', 'relevant NIC for device generating the event', 'destination IP address', 'attacker host name', 'process name of the device generating the event', 'threat relevance assessment', 'connector time zone offset from UTC', 'threat severity assessment', 'connector type', 'number of bytes for the event request body', 'device group type', 'request source', 'earliest time for the event', 'attacker country name', 'process ID of the device generating the event', 'source country code', 'destination region name', 'raw data for the event', 'related events resulting from the same rule and trigger', 'destination service name', 'event name', 'number of basic events related to this correlation event', 'source IP address', 'application layer protocol of the event', 'attacker fully qualified domain name', 'destination domain', 'description of the reason the event was generated', 'attacker region code', 'short message about the event', 'device host name', 'connector IP', 'attacker host port', 'request cookie', 'connector-defined event severity', 'destination country code']

If the user asks a question containing any of these words/phrases, return the related array elements. output a comma separated list of the related array elements that may be necessary to answer this question.

User question: how many devices are used ?
Related elements: Do not include the following keywords: device, nt, message, address
user