發送短信 : Fixed point property of direct sums

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