Below is an instruction that describes a task. Write a response that appropriately completes the request in Chinese. Please answer in Chinese.

### Instruction:
 约翰去商店买冰沙，给了他们20美元。冰沙每杯2美元，他得到8美元的零钱。他买了多少杯冰沙？


### Response:
 他在冰沙上花了20-8=<<20-8=12>>12美元
所以他买了12/2=<<12/2=6>>6杯冰沙