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

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