B'You are given an array a of length n that has a special condition: every element in this array has at most 7 divisors. Find the length of the shortest non-empty subsequence of this array product of whose elements is a perfect square. A sequence a is a subsequence of an array b if a can be obtained from b by deletion of several (possibly, zero or all) elements. The first line contains an integer n ( 1 <= n <= 10^5 ) -- the length of a . The second line contains n integers a_1 , a_2 , ldots , a_{n} ( 1 <= a_i <= 10^6 ) -- the elements of the array a . Output the length of the shortest non-empty subsequence of a product of whose elements is a perfect square. If there are several shortest subsequences, you can find any of them. If there 's no such subsequence, print "-1". In the first sample, you can choose a subsequence [1] . In the second sample, you can choose a subsequence [6, 6] . In the third sample, you can choose a subsequence [6, 15, 10] . In the fourth sample, there is no such subsequence. '...