發送短信 : Automatic linear orders and trees

  ______    ______    _____     _____     _____   
 /_____//  /_   _//  |__  //   |  ___||  / ____|| 
 `____ `    -| ||-     / //    | ||__   / //---`' 
 /___//     _| ||_    / //__   | ||__   \ \\___   
 `__ `     /_____//  /_____||  |_____||  \_____|| 
 /_//      `-----`   `-----`   `-----`    `----`  
 `-`