There is a sequence of numbers. It is known that the second number is 2, the seventh number is 7, and the sum of any three adjacent numbers is 15. What is the 2013th number in this sequence?
有一个数列，已知第2个数是2，第7个数是7，而且任何三个相邻的数的和都是15，那么这个数列中的第2013个数是多少．
<result>6</result>