cube of wood is placed on the table, each side has a number, the sum of the two numbers on the opposite side is equal to 13, Xiao Zhang can see the top and two sides, and the sum of the three numbers he sees is 18 ;Xiao Li can see the top surface and the other two sides, and the sum of the three numbers he sees is 24. So what is the number on the side of the table.
一个正方体木块放在桌子上，每一面都有一个数，位于对面上的两个数之和都等于13，小张能看到顶面和两个侧面，看到的三个数之和是18；小李能看到顶面和另外两个侧面，看到的三个数之和是24．那么贴着桌子这个面的数是多少．
<gadget id="calculator">24 - 26</gadget>
<output>-2</output>

<gadget id="calculator">18 + (-2)</gadget>
<output>16</output>

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

<gadget id="calculator">16 / 2</gadget>
<output>8</output>

<gadget id="calculator">13 - 8</gadget>
<output>5</output>

<result>5</result>