jié zú xiān dēng

捷足先登

the swift-footed get on first

the early bird gets the worm; first come, first served

Example:

二班捷足先登, 把最艰巨的任务抢走了。
Èr bān jiézúxiāndēng, bǎ zuì jiānjù de rènwu qiǎngzǒu le.
Class Two beat the others to the most difficult task