Learn to start from 1, write on the blackboard in the order of 1, 2, 3, 4, 5... until a certain number, Sisi erased one of the numbers, and now the average of the remaining numbers is 11.5, may I ask : What is the number erased by Sisi?
学学从1开始，按1，2，3，4，5…的顺序在黑板上写到某数为止，思思把其中一个数擦掉了，现在剩下的数的平均数是11.5，请问：思思擦掉的数是多少．
<gadget id="calculator">23 * 12</gadget>
<output>276</output>

<gadget id="calculator">22 * 11.5</gadget>
<output>253</output>

<gadget id="calculator">276 - 253</gadget>
<output>23</output>

<result>23</result>