编写一个程序模拟自动售货机。

可以通过向售货机中投入硬币来购买商品。用户从售货机商品列表选择某一商品并投入硬币。如果金额足够，则提供相应商品；如果金额不够，或者该商品已售完，则将硬币退回。维护售货机的工作人员可以为其添加商品或者取走售货款项。

-Write a program to simulate a vending machine.

You can put coins in the vending machine to buy merchandise. The list of goods from the vending machine user to select a commodity and investment coins. If the amount is enough, will provide the corresponding goods　If the amount is not enough, or if the merchandise has been sold out, it will return the coins. Maintenance of vending machines to add staff can take away sales of goods or money