#!/usr/bin/python3
"""
万年历
"""
import datetime
import sys


def is_leap(year):
    """判断闰年"""
    return (year % 4 == 0 and year % 100 != 0) or year % 400 == 0


def get_days(year, month):
    """获得指定月份的天数"""
    days_of_month = [
        0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
    ]
    days = days_of_month[month]
    return days + 1 if is_leap(year) and month == 2 else days


def main():
    """主函数"""
    if len(sys.argv) == 3:
        month = int(sys.argv[1])
        year = int(sys.argv[2])
    else:
        curr_date = datetime.datetime.now()
        year = curr_date.year
        month = curr_date.month
    m = month + 12 if month < 3 else month
    y = year - 1 if month < 3 else year
    c, y = y // 100, y % 100
    w = y + y // 4 + c // 4 - 2 * c + 26 * (m + 1) // 10
    w %= 7
    month_names = [
        '', 'January', 'February', 'March', 'April', 'May', 'June',
        'July', 'August', 'September', 'October', 'November', 'December'
    ]
    print(f'{month_names[month]} {year}'.center(20))
    print('Su Mo Tu We Th Fr Sa')
    print(' ' * 3 * w, end='')
    days = get_days(year, month)
    for day in range(1, days + 1):
        print(f'{day}'.rjust(2), end=' ')
        w += 1
        if w == 7:
            print()
            w = 0
    print()


if __name__ == '__main__':
    main()