AquaMoon and Two Arrays

Description:

Input:

The 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 first line of each test case contains a single integer $$$n$$$ ($$$1 \leq n \leq 100$$$).

The second line of each test case contains $$$n$$$ integers $$$a_1, a_2, \dots, a_n$$$ ($$$0 \leq a_i \leq 100$$$). The sum of all $$$a_i$$$ does not exceed $$$100$$$.

The third line of each test case contains $$$n$$$ integers $$$b_1, b_2, \dots, b_n$$$ ($$$0 \leq b_i \leq 100$$$). The sum of all $$$b_i$$$ does not exceed $$$100$$$.

Output:

For each test case print "-1" on the only line if it is impossible to make two arrays equal with some sequence of operations.

Otherwise, print an integer $$$m$$$ ($$$0 \leq m \leq 100$$$) in the first line — the number of operations. Then print $$$m$$$ lines, each line consists of two integers $$$i$$$ and $$$j$$$ — the indices you choose for the operation.

It can be proven that if it is possible to make two arrays equal with some sequence of operations, there exists a sequence with $$$m \leq 100$$$.

If there are multiple possible solutions, you can print any.

Sample Input:

4
4
1 2 3 4
3 1 2 4
2
1 3
2 1
1
0
0
5
4 3 2 1 0
0 1 2 3 4

Sample Output:

2
2 1
3 1
-1
0
6
1 4
1 4
1 5
1 5
2 5
2 5

Note:

In the first example, we do the following operations:

• $$$i = 2$$$, $$$j = 1$$$: $$$[1, 2, 3, 4] \rightarrow [2, 1, 3, 4]$$$;
• $$$i = 3$$$, $$$j = 1$$$: $$$[2, 1, 3, 4] \rightarrow [3, 1, 2, 4]$$$;

In the second example, it's impossible to make two arrays equal.