發送短信 : Convexity, geodetic, and hull numbers of the join of graphs

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