改用decimal函数，抛弃float函数，彻底解决不精确的问题。
Switch to the decimal function and ditch the float function to solve the imprecision problem once and for all.
改用decimal函数，抛弃float函数，彻底解决不精确的问题。
Switch to the decimal function and ditch the float function to solve the imprecision problem once and for all.