B"You are given two arrays a and b , both consisting of n integers. In one move, you can choose two indices i and j ( 1 <= i, j <= n ; i neq j ) and swap a_i with a_j and b_i with b_j . You have to perform the swap in both arrays. You are allowed to perform at most 10^4 moves (possibly, zero). Can you make both arrays sorted in a non-decreasing order at the end? If you can, print any sequence of moves that makes both arrays sorted. The first line contains a single integer t ( 1 <= t <= 100 ) -- the number of testcases. The first line of each testcase contains a single integer n ( 2 <= n <= 100 ) -- the number of elements in both arrays. The second line contains n integers a_1, a_2, ... , a_n ( 1 <= a_i <= n ) -- the first array. The third line contains n integers b_1, b_2, ... , b_n ( 1 <= b_i <= n ) -- the second array. For each testcase, print the answer. If it's impossible to make both arrays sorted in a non-decreasing order in at most 10^4 moves, print -1. Otherwise, first, print the number of moves k (0 <= k <= 10^4) . Then print i and j for each move (1 <= i, j <= n ; i neq j) . If there are multiple answers, then print any of them. You don't have to minimize the number of moves. "...