Social Media Connection

In a social media application, users can follow one another. You are given the following data: the number of users and a list of pairs representing follow relationships. Write a function to find the number of users that can be reached from a given user through the follow relationships. Input: The first line contains an integer N (the number of users). The second line contains an integer M (the number of follow relationships). The next M lines each contain two integers A and B, meaning user A follows user B. The last line contains the user ID to check the reachability from. Output: A single integer representing the number of users that can be reached, excluding the user itself. Example: Input: 5 4 1 2 1 3 2 4 3 5 1 Output: 4