One operation on a two-digit number means: multiply its two digits, and if you get a one-digit number, write it twice. For example, perform 5 operations on 39 to get 39-27-14-44-16-66. Then how many two-digit numbers become 88 after 4 operations.
对一个两位数进行一次操作是指：将它的两个数字相乘，如果得到一个一位数，则将它写两遍．例如对39进行5次操作依次得到39-27-14一44-16-66．那么经过4次操作变为88的两位数有多少个．
<result>11</result>