B. BAN BANtime limit per test1 secondmemory limit per test256 megabytesinputstandard inputoutputstandard outputYou are given an integer n.Let's define s(n) as the string "BAN" concatenated n times. For example, s(1) = "BAN", s(3) = "BANBANBAN". Note that the length of the string s(n) is equal to 3n.Consider s(n). You can perform the following operation on s(n) any number of times (possibly zero): Select any two distinct indices i and j (1 \leq i, j \leq 3n, i \ne j). Then, swap s(n)_i and s(n)_j. You want the string "BAN" to not appear in s(n) as a subsequence. What's the smallest number of operations you have to do to achieve this? Also, find one such shortest sequence of operations.A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.InputThe input consists of multiple test cases. The first line contains a single integer t (1 \leq t \leq 100)  — the number of test cases. The description of the test cases follows.The only line of each test case contains a single integer n (1 \leq n \leq 100).OutputFor each test case, in the first line output m (0 \le m \le 10^5) — the minimum number of operations required. It's guaranteed that the objective is always achievable in at most 10^5 operations under the constraints of the problem. Then, output m lines. The k-th of these lines should contain two integers i_k, j_k (1\leq i_k, j_k \leq 3n, i_k \ne j_k) denoting that you want to swap characters at indices i_k and j_k at the k-th operation. After all m operations, "BAN" must not appear in s(n) as a subsequence. If there are multiple possible answers, output any.ExampleInput
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Output
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NoteIn the first testcase, s(1) =  "BAN", we can swap s(1)_1 and s(1)_2, converting s(1) to "ABN", which does not contain "BAN" as a subsequence.In the second testcase, s(2) =  "BANBAN", we can swap s(2)_2 and s(2)_6, converting s(2) to "BNNBAA", which does not contain "BAN" as a subsequence.
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1 1 2 1 2 6 
['constructive algorithms', '*900']