Bracketing frenzy ....oracle

I just found myself decyphering this:

SELECT ...
FROM report_results rpt
WHERE NOT ( (substr(rpt.report_type,2,1) in ('1','2','3','4','5')) and
         (rpt.sig_type = 'ISDNMA') and
         ((rpt.group_ctn != rpt.ctn_prefix||rpt.ctn_suffix) and
          (length(rpt.group_ctn) != length(rpt.ctn_prefix||rpt.ctn_suffix)) and
          ((length(rpt.group_ctn) != (length(rpt.ctn_prefix||rpt.ctn_suffix)-1)
          ))));

Which turns out to mean this:

SELECT ...
FROM   report_results rpt
WHERE  NOT (     SUBSTR(rpt.report_type,2,1) IN ('1','2','3','4','5')
           AND  rpt.sig_type = 'ISDNMA'
           AND  rpt.group_ctn != rpt.ctn_prefix||rpt.ctn_suffix
           AND  LENGTH(rpt.group_ctn) != LENGTH(rpt.ctn_prefix||rpt.ctn_suffix)
           AND  LENGTH(rpt.group_ctn) != LENGTH(rpt.ctn_prefix||rpt.ctn_suffix)-1 );

No wonder there are no brackets left in the shops.