The school has 67 footballs, basketballs, and volleyballs. Among them, the number of basketballs is 1 times more than footballs, and the number of volleyballs is 1 times more than basketballs. How many footballs are there?
学校有足球、篮球、排球共67个，其中篮球的个数比足球的2倍多1个，排球的个数比篮球的2倍多1，足球有多少个？
<gadget id="calculator">67 - 1 - 2 - 1</gadget>
<output>63</output>

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

<gadget id="calculator">1 + 2 + 4</gadget>
<output>7</output>

<gadget id="calculator">63 / 7</gadget>
<output>9</output>

<result>9</result>