發送短信 : Fixed point property of direct sums

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