实现删除嵌套的注释。每次从键盘上读取三行字符串。若发现存在嵌套的情况，即在注释内又存在的/*或*/，就把这/*或*/删除，注释外的部分保留。/与*优先级是左结合，即当前出现/*/时，优先删除/*。-Achieve delete nested comments. Each read three lines of string from the keyboard. If it is found of the presence of nested, the comment /* or* /, put