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

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發送短信 : Natural Partial Orders on Transformation Semigroups with Fixed Sets