def login():
    loop = 1
    while loop == 1:
        a = raw_input("Enter a username: ")
        a = a.lower()
        if a in logins:
            print "That username is already taken!"
            print ""
        else:
            b = raw_input("Enter a password: ")
            b = b.lower()
            logins[a] = b
            loop = 0
            return ""



logins={'jim':'lemon99'}
loop = 1

print login()

while loop == 1:
    print ""
    print "Login"
    username = raw_input("Enter your username: ")
    if username in logins:
        password = raw_input("Enter your password: ")
        if  password == logins[username]:
            print "Thank you"
            loop = 0
        else:
            print "That is an invalid password"
    else:
        print "There is no such user"