B'AquaMoon and Cirno are playing an interesting game with arrays. Cirno has prepared two arrays a and b , both consist of n non-negative integers. AquaMoon can perform the following operation an arbitrary number of times (possibly zero): AquaMoon wants to make some operations to make arrays a and b equal. Two arrays a and b are considered equal if and only if a_i = b_i for all 1 <= q i <= q n . Help AquaMoon to find a sequence of operations that will solve her problem or find, that it is impossible to make arrays a and b equal. Please note, that you don 't have to minimize the number of operations. The input consists of multiple test cases. The first line contains a single integer t ( 1 <= q t <= q 100 ) -- the number of test cases. The first line of each test case contains a single integer n ( 1 <= q n <= q 100 ). The second line of each test case contains n integers a_1, a_2, ... , a_n ( 0 <= q a_i <= q 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, ... , b_n ( 0 <= q b_i <= q 100 ). The sum of all b_i does not exceed 100 . 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 <= q m <= q 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 <= q 100 . If there are multiple possible solutions, you can print any. In the first example, we do the following operations: In the second example, it 's impossible to make two arrays equal. '...