How Do I Know the classnum of the material for BAPI_OBJCL_CREATE

Hello,

Someone Knows How to get the classnum of the material? I don't know what value should I put for the parameter of the BAPI  BAPI_OBJCL_CREATE

 
            CALL FUNCTION 'BAPI_OBJCL_CREATE'
              EXPORTING
                OBJECTKEYNEW    = class-object
                OBJECTTABLENEW  = class-objecttable
                CLASSNUMNEW     = ????

                CLASSTYPENEW    = class-classtype
              TABLES
                RETURN          = returnmessages.

Thank you so much