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

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發送短信 : On r-cross intersecting families of sets