From the 49 consecutive natural numbers 1 to 49, select several numbers and arrange them in a circle so that the product of any two adjacent numbers is less than 100. How many numbers can you pick at most?
从连续的49个自然数1～49中，挑出若干个数排成一个圆圈，使相邻的任意两个数的乘积都小于100，最多能挑出多少个数来．
<result>18</result>