The size of shoes is usually in "yard" or "centimeter", and the conversion relationship between them is b=2a-10 (b indicates the number of yards, a indicates the number of centimeters), then how many centimeters is the length of a 40-yard shoe.
鞋的尺码通常用"码"或"厘米"作单位，它们之间的换算关系是b=2a-10(b表示码数，a表示厘米数)，那么40码的鞋长多少厘米．
<result>25</result>