Dad queues up to buy movie tickets, counting from front to back, he is the 4th, and counting from back to front, he is also the 4th, how many people line up to buy movie tickets?
爸爸排队买电影票，从前往后数，他是第4个，从后往前数，他也是第4个，一共有多少个人排队买电影票．
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">4 + 3</gadget>
<output>7</output>

<result>7</result>