發送短信 : Existence of independent [1, 2]-sets in caterpillars

 ______    __   __              _____   __    __  
|      \\  \ \\/ //     ___    |  ___|| \ \\ / // 
|  --  //   \ ` //     /   ||  | ||__    \ \/ //  
|  --  \\    | ||     | [] ||  | ||__     \  //   
|______//    |_||      \__ ||  |_____||    \//    
`------`     `-`'       -|_||  `-----`      `     
                         `-`