def main(): # This is the program for Question 1
    BD = {}
    done = False
    while not done:
        date = input( "Give me  a date: " )
        if date == "":
            done = True
        else:
            person = input( "Whose birthday? " )
            if date in BD.keys():
                BD[date].append(person)
            else:
                BD[date] = [person]
    done = False
    while not done:
        birthday = input( "Give me a birthday: " )
        if birthday == "":
            done = True
        elif birthday in BD.keys():
            print( BD[birthday] )
        else:
            print( "I don't know anyone with a birthday then." )

def lowerCase(s):
    s1 = ""
    alphabet = "abcdefghijklmnopqrstuvwxyz"
    for letter in s:
        if letter in alphabet:
            s1 = s1+letter
    return s1


main()