In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.

Example Input: XjYkMfARxWBSBjuXyDrFt, EtUxIfiHkMfARxWBSckTLTTnR
Example Output: kMfARxWBS

Example Input: TnHJcxtwcZ, XFdHJcxNKw
Example Output: HJcx

Example Input: JNUXooNwUqNOTQbKQdCxq, fcHNmMzoNwUqNOTqSNATAZ
Example Output:
oNwUqNOT