输入某年某月某日，判断这一天是这一年的第几天。例如，2001年3月5日是这一年的第64天。 要求：使用分支结构语句实现。(Enter a certain year and a certain day to judge the day is the first day of the year. For example, March 5, 2001 was the sixty-fourth day of the year. Requirement: use branch structure st