The problem seems to be on the GCD for me. Just building the GCD matrix alone fails efficiency. Do you need to be a GCD expert to solve this? There must be some theorem or something that is required. I can't pass the effiencny tests. How can I make it faster?

python 3: not solve from test 6 bc exceed time.

        # Write your code here
        appe_list = []
        for i in range(r2-r1+1):
            for j in range(c2-c1+1):
                appe_list.append(gcd(a[r1+i],b[c1+j]))
        print(len(set(appe_list)))  

Here is my solution in java, javascript, python, C, C++, Csharp HackerRank GCD Matrix Problem Solution

Here is GCD matrix problem solution - https://programs.programmingoneonone.com/2021/07/hackerrank-GCD-matrix-problem-solution.html

If you know about Mobius function and Inclusive-Exclusive Principle, solving this problem is more comfortable !