first come first served
先到先得，按顺序依次服务
口语·书面·表示先到先得
英文释义
the principle or practice of allocating resources or benefits based on the order in which they are requested or obtained
例句
The free tickets are limited, so it's first come first served at the box office.
典故来源
源自商业和服务业，最早到达的顾客最早得到服务，强调按到达顺序分配资源。