發送短信 : On cyclic sums for polygons

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