weekday=["Sunday","Monday","Tuesday","Wednesday","Thursday", "Friday","Saturday"]
def ymd(year,month,day):
    m_day=[0,31,28,31,30,31,30,31,31,30,31,30,31]
    days=0
    year=abs(year)
    for i in range(0,year):
        if i%400==0 or (i%4==0 and i%100!=0 ):
            days+=366
        else:
            days+=365
    if  (year%400==0 or (year%4==0 and year%100!=0 )):
        m_day[2]=29
......................

weekday=["Sunday","Monday","Tuesday","Wednesday","Thursday", "Friday","Saturday"]
def ymd(year,month,day):
    m_day=[0,31,28,31,30,31,30,31,31,30,31,30,31]
    days=0
    for i in range(year):
        if i%400==0 or (i%4==0 and i%100!=0 ):
            days+=366
        else:
            days+=365
    for  k  in range(1,month):
        days+=m_day[k]
        if k==2 and   (year%400==0 or (year%4==0 and year%100!=0 )):
......................

weekday=["Sunday","Monday","Tuesday","Wednesday","Thursday", "Friday","Saturday"]
days=0
m_day=[31,28,31,30,31,30,31,31,30,31,30,31]
for i in range(2020):
    if i%400 or (i%4==0 and i%100!=0):
        days+=366
    else:
        days+=365
for k in range(11):
    days+=m_day[k]
t_days=days+18+1     #2020-11-18
print(t_days%7)
......................