Dongdong's home is 3 kilometers away from the school. This morning, after walking 1 kilometer to school, Dongdong found that the red scarf was not on, so he hurried home to get the red scarf before going to school. This morning, how many kilometers did Dongdong walk to school?
冬冬的家到学校一共有3千米．这天早上，冬冬上学走了1千米后发现红领巾没戴，连忙回家取红领巾再去上学．这天早上，冬冬上学一共走了多少千米．
<gadget id="calculator">1 + 1 + 3</gadget>
<output>5</output>

<result>5</result>