CF1370B.GCD Compression

传统题 时间 2000 ms 内存 256 MiB 5 尝试 1 已通过 1 标签

GCD Compression

Ashish has an array aa of consisting of 2n2n positive integers. He wants to compress aa into an array bb of size n1n-1. To do this, he first discards exactly 22 (any two) elements from aa. He then performs the following operation until there are no elements left in aa:

  • Remove any two elements from aa and append their sum to bb.

The compressed array bb has to have a special property. The greatest common divisor (gcd\mathrm{gcd}) of all its elements should be greater than 11.

Recall that the gcd\mathrm{gcd} 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 aa into an array bb of size n1n-1 such that gcd(b1,b2...,bn1)>1gcd(b_1, b_2..., b_{n-1}) \gt 1.

Help Ashish find a way to do so.

Input

The first line contains a single integer tt (1t101 \leq t \leq 10) — the number of test cases. The description of the test cases follows.

The first line of each test case contains a single integer nn (2n10002 \leq n \leq 1000).

The second line of each test case contains 2n2n integers a1,a2,,a2na_1, a_2, \ldots, a_{2n} (1ai10001 \leq a_i \leq 1000) — the elements of the array aa.

Output

For each test case, output n1n-1 lines — the operations performed to compress the array aa to the array bb. The initial discard of the two elements is not an operation, you don't need to output anything about it.

The ii-th line should contain two integers, the indices (11 —based) of the two elements from the array aa that are used in the ii-th operation. All 2n22n-2 indices should be distinct integers from 11 to 2n2n.

You don't need to output two initially discarded elements from aa.

If there are multiple answers, you can find any.

Note

In the first test case, b={3+6,4+5}={9,9}b = \{3+6, 4+5\} = \{9, 9\} and gcd(9,9)=9\mathrm{gcd}(9, 9) = 9.

In the second test case, b={9+10}={19}b = \{9+10\} = \{19\} and gcd(19)=19\mathrm{gcd}(19) = 19.

In the third test case, b={1+2,3+3,4+5,90+3}={3,6,9,93}b = \{1+2, 3+3, 4+5, 90+3\} = \{3, 6, 9, 93\} and gcd(3,6,9,93)=3\mathrm{gcd}(3, 6, 9, 93) = 3.

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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