B'A string s of length n , consisting of lowercase letters of the English alphabet, is given. You must choose some number k between 0 and n . Then, you select k characters of s and permute them however you want. In this process, the positions of the other n-k characters remain unchanged. You have to perform this operation exactly once. For example, if s= texttt{"andrea"} , you can choose the k=4 characters texttt{"a_d_ea"} and permute them into texttt{"d_e_aa"} so that after the operation the string becomes texttt{"dneraa"} . Determine the minimum k so that it is possible to sort s alphabetically (that is, after the operation its characters appear in alphabetical order). The first line contains a single integer t ( 1 <= t <= 1000 ) -- the number of test cases. Then t test cases follow. The first line of each test case contains one integer n ( 1 <= n <= 40 ) -- the length of the string. The second line of each test case contains the string s . It is guaranteed that s contains only lowercase letters of the English alphabet. For each test case, output the minimum k that allows you to obtain a string sorted alphabetically, through the operation described above. In the first test case, we can choose the k=2 characters texttt{"_ol"} and rearrange them as texttt{"_lo"} (so the resulting string is texttt{"llo"} ). It is not possible to sort the string choosing strictly less than 2 characters. In the second test case, one possible way to sort s is to consider the k=6 characters texttt{"_o__force_"} and rearrange them as texttt{"_c__efoor_"} (so the resulting string is texttt{"ccdeefoors"} ). One can show that it is not possible to sort the string choosing strictly less than 6 characters. In the third test case, string s is already sorted (so we can choose $'...