發送短信 : The Ising chain constrained to an even or odd number of positive spins

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