1 If the sun goes in, it becomes hidden from view by clouds. -- (太阳)被云遮住
2 If a fact or piece of information goes in, you understand it or remember it. -- 被理解,被领会;被记住
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.
再长的路,一步步也能走完,再短的路,不迈开双脚也无法到达。