The bottom of the shoe is generally marked with the length of the shoe. The shoe size marked with "21" is 32; the shoe size marked with "24" is 38; the shoe size marked with "25" is 40; What is the shoe size of "26.5".
鞋的底部一般都标有鞋子的长度，标有"21"的鞋码是32号；标有"24"的鞋码是38号；标有"25"的鞋码是40号；那么标有"26.5"的鞋码是多少号．
<gadget id="calculator">26.5 * 2</gadget>
<output>53</output>

<gadget id="calculator">53 - 10</gadget>
<output>43</output>

<result>43</result>