Charitable donations raise money to build a library, which can be returned year by year later. According to the personal database, some charitable donation projects have set the rule of "returning by stages every year", that is, donors can choose to recover part or all of the donated funds year by year within a few years after donation. The advantage of this is that it can alleviate the financial pressure of donors to a certain extent, and at the same time ensure the long-term stable operation of charitable donation projects.