發送短信 : The graph relabeling problem and its variants

 __   _      ___      ______     ___     _    _   
| || | ||   / _ \\   /_   _//   / _ \\  | || | || 
| '--' ||  | / \ ||  `-| |,-   | / \ || | || | || 
| .--. ||  | \_/ ||    | ||    | \_/ || | \\_/ || 
|_|| |_||   \___//     |_||     \___//   \____//  
`-`  `-`    `---`      `-`'     `---`     `---`