The sum of the ages of a group of children is 54 years old, the oldest one is 13 years old and the other is 8 years old. Except for this 8-year-old child, the age of the other children can just form an arithmetic progression, then how many children are there in this group?
有一群儿童的年龄之和为54岁，其中最大的13岁，另一个8岁．除去这个8岁儿童外，其余儿童的年龄恰好能组成一个等差数列，则这群儿童至少有多少名．
<result>5</result>