Xiaohua went to the bookstore to buy notebooks, and he bought 5.7 yuan a copy, which was 0.4 yuan short, so he had to buy 4.15 yuan a copy, and the remaining money was just enough to buy a ballpoint pen. How much is this ballpoint pen?
小华到书店买笔记本，买5.7元一本差0.4元，他只好买4.15元一本的，剩下的钱正好买一枝圆珠笔．这枝圆珠笔多少元？
<gadget id="calculator">5.7 - 0.4 - 4.15</gadget>
<output>1.15</output>

<result>1.15</result>