write a go solution for Description:
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.

Input Format:
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 Format:
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".

Note:
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.. Output only the code with no comments, explanation, or additional text.