There are 20 questions in a math test. It is stipulated that 2 points will be awarded for a correct answer, 1 point will be deducted for a wrong answer, and no points will be awarded for unanswered questions. Xiao Ming scored 23 points. It is known that the number of unanswered questions is an even number. So how many times did he answer wrong?
一次数学考试共有20道题．规定答对一题得2分，答错一题扣1分，未答的题不得分．小明得了23分，已知他未答的题目数是偶数．那么他答错了多少道．
<gadget id="calculator">13 * 2</gadget>
<output>26</output>

<gadget id="calculator">26 - 23</gadget>
<output>3</output>

<result>3</result>