class GoodsStock {
    String goodsCode;

    int stockNum;

    GoodsStock(String code, int num) {
      goodsCode = code;
      stockNum = num;
    }

    void addStock(int amount) {
     stockNum += amount;
    }

    int subtractStock(int amount) {
      if(stockNum < amount)
          return 0;
      stockNum -= amount;
         return amount;
  }
}