There are several balls in the box, and Oou takes out half of the box each time and puts back a ball, which counts as one operation. He operated a total of 3 times, and there are 3 balls in the bag. How many balls are in the bag.
盒子里有若干个球，欧欧每次拿出盒中的一半再放回一个球，这样算操作一次．他一共操作了3次，袋中还有3个球．袋中原来有多少个球．
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<gadget id="calculator">6 - 1</gadget>
<output>5</output>

<gadget id="calculator">2 * 5</gadget>
<output>10</output>

<result>10</result>