There are four natural numbers, starting from the second number, each number is 3 greater than the previous number. It is known that the average of these four numbers is 24.5, what is the largest number among them.
有四个自然数，从第二个数起，每个数都比前一个数大3．已知这四个数的平均数是24.5，其中最大一个数是多少．
<result>29</result>