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

Example Input: TnHJcxtwcZ, XFdHJcxNKw
Example Output: HJcx

Example Input: tyVlHfTPLRSdFilXnSfqQ, bkTPLRSdFiMgXC
Example Output: TPLRSdFi

Example Input: ZpyzSpxCZQAcvAzEbVpDriQpx, IoxCZQAcvAzEgUrt
Example Output:
xCZQAcvAzE