B'You are given two integers n and k along with a string s . Your task is to check whether all possible strings of length n that can be formed using the first k lowercase English alphabets occur as a subsequence of s . If the answer is NO, you also need to print a string of length n that can be formed using the first k lowercase English alphabets which does not occur as a subsequence of s . If there are multiple answers, you may print any of them. Note: A string a is called a subsequence of another string b if a can be obtained by deleting some (possibly zero) characters from b without changing the order of the remaining characters. The first line of input contains a single integer t , (1 <= t <= 10^5) , the number of test cases. The first line of each test case contains 3 integers n , (1 <= n <= 26), : k , (1 <= k <= 26), : m , (1 <= m <= 1000) , where n and k are the same as described in the input and m is the length of the string s . The second line of each test case contains a single string s of length m , comprising only of the first k lowercase English alphabets. It is guaranteed that the sum of m and the sum of n over all test cases does not exceed 10^6 . For each test case, print YES if all possible strings of length n that can be formed using the first k lowercase English alphabets occur as a subsequence of s , else print NO. If your answer is NO, print a string of length n that can be formed using the first k lowercase English alphabets which does not occur as a subsequence of s in the next line. You may print each letter of YES or NO in any case (for example, YES, yES, YeS will all be recognized as a positive answer). For the first test case, all possible strings (aa, ab, ba, bb) of length 2 that can be formed using the first 2 English alphab'...