CF1869A Make It Zero

During Zhongkao examination, Reycloer met an interesting problem, but he cannot come up with a solution immediately. Time is running out! Please help him. Initially, you are given an array $ a $ consisting of $ n \ge 2 $ integers, and you want to change all elements in it to $ 0 $ . In one operation, you select two indices $ l $ and $ r $ ( $ 1\le l\le r\le n $ ) and do the following: - Let $ s=a_l\oplus a_{l+1}\oplus \ldots \oplus a_r $ , where $ \oplus $ denotes the [bitwise XOR operation](https://en.wikipedia.org/wiki/Bitwise_operation#XOR); - Then, for all $ l\le i\le r $ , replace $ a_i $ with $ s $ . You can use the operation above in any order at most $ 8 $ times in total. Find a sequence of operations, such that after performing the operations in order, all elements in $ a $ are equal to $ 0 $ . It can be proven that the solution always exists.

The first line of input contains a single integer $ t $ ( $ 1\le t\le 500 $ ) — the number of test cases. The description of test cases follows. The first line of each test case contains a single integer $ n $ ( $ 2\le n\le 100 $ ) — the length of the array $ a $ . The second line of each test case contains $ n $ integers $ a_1,a_2,\ldots,a_n $ ( $ 0\le a_i\le 100 $ ) — the elements of the array $ a $ .

For each test case, in the first line output a single integer $ k $ ( $ 0\le k\le 8 $ ) — the number of operations you use. Then print $ k $ lines, in the $ i $ -th line output two integers $ l_i $ and $ r_i $ ( $ 1\le l_i\le r_i\le n $ ) representing that you select $ l_i $ and $ r_i $ in the $ i $ -th operation. Note that you do not have to minimize $ k $ . If there are multiple solutions, you may output any of them.

In the first test case, since $ 1\oplus2\oplus3\oplus0=0 $ , after performing the operation on segment $ [1,4] $ , all the elements in the array are equal to $ 0 $ . In the second test case, after the first operation, the array becomes equal to $ [3,1,4,15,15,15,15,6] $ , after the second operation, the array becomes equal to $ [0,0,0,0,0,0,0,0] $ . In the third test case: Operation $ a $ before $ a $ after $ 1 $ $ [\underline{1,5},4,1,4,7] $ $ \rightarrow $ $ [4,4,4,1,4,7] $ $ 2 $ $ [4,4,\underline{4,1},4,7] $ $ \rightarrow $ $ [4,4,5,5,4,7] $ $ 3 $ $ [4,4,5,5,\underline{4,7}] $ $ \rightarrow $ $ [4,4,5,5,3,3] $ $ 4 $ $ [\underline{4,4,5},5,3,3] $ $ \rightarrow $ $ [5,5,5,5,3,3] $ $ 5 $ $ [5,5,5,\underline{5,3,3}] $ $ \rightarrow $ $ [5,5,5,5,5,5] $ $ 6 $ $ [\underline{5,5,5,5,5,5}] $ $ \rightarrow $ $ [0,0,0,0,0,0] $ In the fourth test case, the initial array contains only $ 0 $ , so we do not need to perform any operations with it.