#!perl -l print map{$x=$a.$x;$e||=chop$x;--$e?$a:($a^=$b)^$b}2..pop,$b=pop^($a=pop)
#!perl -l ($a,$b,$c)=@ARGV;for(;;){for(1..$/[$/++]||$a){(print@/),exit if$c==push@/,$a}($b,$a)=($a,$b)}