Xiaoping's home is 2 kilometers away from the school. Once he walked 1 kilometer to school, remembering that he had forgotten his pencil case, he went home to get it. How many kilometers did he walk to school this time?
小平家距学校2千米，一次他上学走了1千米，想起忘带铅笔盒，又回家去取．这次他到学校共走了多少千米？
<gadget id="calculator">1 * 2</gadget>
<output>2</output>

<gadget id="calculator">2 + 2</gadget>
<output>4</output>

<result>4</result>