Can somebody plz explain the approach to this problem.
I have got partial in it.
I have no idea how to get full AC in it.
Chef has a sequence of positive integers A1,A2,…,AN. He wants to split this sequence into two non-empty (not necessarily contiguous) subsequences B and C such that GCD(B)+GCD(C) is maximum possible. Help him find this maximum value.
Note: The greatest common divisor (GCD) of a sequence of positive integers is the largest positive integer that divides each element of this sequence. For example, the GCD of the sequence (8,12) is 4.
The first line of the input contains a single integer T denoting the number of test cases. The description of T test cases follows.
The first line of each test case contains a single integer N.
The second line contains N space-separated integers A1,A2,…,AN.
For each test case, print a single line containing one integer — the maximum value of GCD(B)+GCD(C).
1≤Ai≤109 for each valid i
Subtask #1 (20 points): 2≤N≤20
Subtask #2 (80 points): original constraints
4 4 7 6
Example case 1: For example, the sequence A can be divided into subsequences B=(4,4,6) and C=(7)