CF1993A Question Marks

Tim is doing a test consisting of $ 4n $ questions; each question has $ 4 $ options: 'A', 'B', 'C', and 'D'. For each option, there are exactly $ n $ correct answers corresponding to that option — meaning there are $ n $ questions with the answer 'A', $ n $ questions with the answer 'B', $ n $ questions with the answer 'C', and $ n $ questions with the answer 'D'. For each question, Tim wrote his answer on the answer sheet. If he could not figure out the answer, he would leave a question mark '?' for that question. You are given his answer sheet of $ 4n $ characters. What is the maximum number of correct answers Tim can get?

The first line contains a single integer $ t $ ( $ 1 \le t \le 1000 $ ) — the number of test cases. The first line of each test case contains an integer $ n $ ( $ 1 \le n \le 100 $ ). The second line of each test case contains a string $ s $ of $ 4n $ characters ( $ s_i \in \{\texttt{A}, \texttt{B}, \texttt{C}, \texttt{D}, \texttt{?}\} $ ) — Tim's answers for the questions.

For each test case, print a single integer — the maximum score that Tim can achieve.

In the first test case, there is exactly one question with each answer 'A', 'B', 'C', and 'D'; so it's possible that Tim gets all his answers correct. In the second test case, there are only two correct answers 'A' which makes him get exactly $ 2 $ points in any case. In the third test case, Tim can get at most $ 2 $ correct answers with option 'A' and $ 2 $ correct answers with option 'B'. For example, he would get $ 4 $ points if the answers were 'AACCBBDD'. In the fourth test case, he refuses to answer any question at all, which makes him get $ 0 $ points.