【PTA A1069】1069 The Black Hole of Numbers (20)(20 分)
Forany4-digitintegerexcepttheoneswithallthedigitsbeingthesame,ifwesortthedigitsinnon-increasingorderfirst,andtheninnon-decreasingorder,anewnumbercanbeobtainedbytakingthesecondnumberfromthefirstone.Rep