def CheckMystery():
    Mystery = False
    Quotient = (YYYY / 400)
    Remainder = (YYYY - (400 * Quotient))
    if Remainder == 0:
        Mystery = False
    else:
        Quotient = (YYYY / 100)
        Remainder = (YYYY - (100 * Quotient))
        if Remainder >= 0:
            Quotient = (YYYY / 4)
            Remainder = (YYYY - (4 * Quotient))
            if Remainder == 0:
                Mystery = False

def DisplayResults():
    if Error_Found == True:
        print ("Error! Please try again.")

if __name__ == "__main__":
    DD = int(input("Enter day number: "))
    MM = int(input("Enter month number: "))
    YYYY = int(input("Enter year number: "))

    if MM == [4, 6, 9, 11]:
        Last_Day = 30
    elif MM == [1, 3, 5, 8, 10, 12]:
        Last_Day = 31
    elif MM == 2:
        CheckMystery()
    else:
        Error_Found = True

    if Error_Found == False:
        if DD < 1 or DD > Last_Day:
            Error_Found = True

DisplayResults()