發送短信 : A uniformly most powerful cumulative sum scheme based on symmetry

            ______   _____       ___     _    _   
    ___    /_   _// |  __ \\    / _ \\  | \  / || 
   /   ||   -| ||-  | |  \ ||  | / \ || |  \/  || 
  | [] ||   _| ||_  | |__/ ||  | \_/ || | .  . || 
   \__ ||  /_____// |_____//    \___//  |_|\/|_|| 
    -|_||  `-----`   -----`     `---`   `-`  `-`  
     `-`