输入年月如：2001（回车）6，打印出该月的月历。不过如果输入的是1800年之前的年月，会出现错误。只能显示1800年以后的月历。-Enter the year, such as: 2001 (carriage return) 6, print out the calendar for the month. However, if the input is 1800 years before, there will be errors. After 1800 can only display a