Remove a number from 1 to 9, select two different numbers from the remaining eight numbers and arrange them to get a two-digit number. If there are 21 multiples of 2, 12 multiples of 4, and 7 There are 8 multiples, ask for the number that was removed at the beginning.
从1到9中去掉一个数字，从这剩下的八个数字选出两个不同的数字排列起来得到的二位数中，如果2的倍数有21个，4的倍数有12个，7的倍数有8个，请求出最开始去掉的那个数字．
<result>8</result>