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CF1370B.GCD Compression
GCD Compression
Ashish has an array of consisting of positive integers. He wants to compress into an array of size . To do this, he first discards exactly (any two) elements from . He then performs the following operation until there are no elements left in :
- Remove any two elements from and append their sum to .
The compressed array has to have a special property. The greatest common divisor () of all its elements should be greater than .
Recall that the of an array of positive integers is the biggest integer that is a divisor of all integers in the array.
It can be proven that it is always possible to compress array into an array of size such that .
Help Ashish find a way to do so.
Input
The first line contains a single integer () — the number of test cases. The description of the test cases follows.
The first line of each test case contains a single integer ().
The second line of each test case contains integers () — the elements of the array .
Output
For each test case, output lines — the operations performed to compress the array to the array . The initial discard of the two elements is not an operation, you don't need to output anything about it.
The -th line should contain two integers, the indices ( —based) of the two elements from the array that are used in the -th operation. All indices should be distinct integers from to .
You don't need to output two initially discarded elements from .
If there are multiple answers, you can find any.
Note
In the first test case, and .
In the second test case, and .
In the third test case, and .
Samples
3
3
1 2 3 4 5 6
2
5 7 9 10
5
1 3 3 4 5 90 100 101 2 3
3 6
4 5
3 4
1 9
2 3
4 5
6 10
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