def ask_user(question, choice_1, choice_2, error_msg):
    letsplay = False
    print question + ' ('+ choice_1 + '=yes, ' + choice_2 + '=no):'
    answer = raw_input()
    while letsplay == False:
        if answer == choice_1 or choice_2:
            if answer == choice_1:
                letsplay = True
                break
            elif answer == choice_2:
                letsplay = False
                print 'Quitting game.'
                sys.exit()
            else:
                print error_msg
                answer = raw_input()
    return answer