發送短信 : Fixed points for multivalued mappings and the metric completeness

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