def main():
print("<STR_LIT>")<EOL>while True:<EOL><INDENT>user_input = input("<STR_LIT>")<EOL>if user_input == "<STR_LIT>":<EOL><INDENT>break<EOL><DEDENT>try:<EOL><INDENT>print("<STR_LIT>".format(evaluate(user_input)))<EOL><DEDENT>except Exception:<EOL><INDENT>print("<STR_LIT>")<EOL>user_input = input("<STR_LIT>")<EOL><DEDENT><DEDENT>print("<STR_LIT>")<EOL>
simple user-interface