B'You are given a string s consisting of lowercase English letters and a number k . Let 's call a string consisting of lowercase English letters beautiful if the number of occurrences of each letter in that string is divisible by k . You are asked to find the lexicographically smallest beautiful string of length n , which is lexicographically greater or equal to string s . If such a string does not exist, output -1 . A string a is lexicographically smaller than a string b if and only if one of the following holds: The first line contains a single integer T ( 1 <= T <= 10 ,000 ) -- the number of test cases. The next 2 cdot T lines contain the description of test cases. The description of each test case consists of two lines. The first line of the description contains two integers n and k ( 1 <= k <= n <= 10^5 ) -- the length of string s and number k respectively. The second line contains string s consisting of lowercase English letters. It is guaranteed that the sum of n over all test cases does not exceed 10^5 . For each test case output in a separate line lexicographically smallest beautiful string of length n , which is greater or equal to string s , or -1 if such a string does not exist. In the first test case "acac" is greater than or equal to s , and each letter appears 2 or 0 times in it, so it is beautiful. In the second test case each letter appears 0 or 1 times in s , so s itself is the answer. We can show that there is no suitable string in the third test case. In the fourth test case each letter appears 0 , 3 , or 6 times in "abaabaaab". All these integers are divisible by 3 . '...