Pergunta de entrevista da empresa PayPal

Given number pattern. If we repeat the number one by one in each phase when the same number series will get? Example: 2,3,6,7,9 First repetitive 3,6,7,9,2( moved 2 here) Next repetitive 6,7,9,2,3(moved 3 here) And so on ... When we will get again 2,3,6,7,9 . Same case with millions of numbers. Write an algorithm for it