0 something or someone that acts as an early and less advanced model for what will appear in the future, or a warning or sign of what is to follow -- 先驱,先行者;预兆,前兆
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。