摘要：For a positive integer N , the digit sum of N is defined as the sum of N itself and its digits. When M is the digitsum of N , we call N a generator of 阅读全文

摘要：An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. The molar mass of an organic compound is the 阅读全文

摘要：You have devised a new encryption technique which encodes a message by inserting between its characters randomly generated strings in a clever way. Be 阅读全文

摘要：Trung is bored with his mathematics homeworks. He takes a piece of chalk and starts writing a sequence of consecutive integers starting with 1 to N <t 阅读全文

摘要：There is an objective test result such as ``OOXXOXXOOO". An `O' means a correct answer of a problem and an `X' means a wrong answer. The score of each 阅读全文