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

Example Input: FSwxBJ, iTwxAa
Example Output: wx

Example Input: TnHJcxtwcZ, XFdHJcxNKw
Example Output: HJcx

Example Input: YqChtrOThFEO, szTrOThFKaIM
Example Output:
rOThF