sub f{
my@a;
"@_"=~/(.)(.*)(?!\1)(.)(.*)\3(?{push@a,[$1.$3x2,"$`$2$4$'"]})^/;
my$s=0;
#$s+=$-=$$_[0]-$s+f($$_[1])for@a;
#$s<($x=$$_[0]+f($$_[1]))&&($s=$x)for@a;
$s<($x=$$_[0]+0+f($$_[1].''))&&($s=$x)for@a;
$s;
}
print f<>