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## 문제

Ms. Garrette needs help grading her multiple choice exams. To prevent cheating, she gave each student an individualized exam. She wants to write a program that, given an answer key and a particular student’s responses, calculates the number of incorrect answers. Can you help her?

## 입력

The first line of input is the number of test cases that follow. Each test case starts with an integer L (0 < L ≤ 100) representing the number of questions on the exam. The next line contains the answer key, where each question is represented by a single letter (i.e. a, b, c, or d) corresponding to the correct answer. The following line contains the student’s responses in the same format.

## 출력

For each case, output the line “Case x:” where x is the case number, on a single line. This is followed by the number of student responses that did not match the answer key.

## 예제 입력 1

2
5

Case 1: 1