Exam

Your friend and you took a true/false exam of n questions. You know your answers, your friend's answers, and that your friend got k questions correct.

Compute the maximum number of questions you could have gotten correct.

The first line of input will contain a single integer m that indicates the number datasets to follow. Each dataset begins with a single integer k. The second line in the dataset contains a string of n (1 ≤ n ≤ 1000) characters, the answers you wrote down. Each letter is either a ‘T’ or an ‘F’. The third line in the dataset contains a string of n characters, the answers your friend wrote down. Each letter is either a ‘T’ or an ‘F’. The input will satisfy 0 ≤ k ≤ n.

For each dataset print, on one line, the maximum number of questions you could have gotten correct.