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

Example Input: wCfNCfxvLRAxBstRTwMSqTn, AhwxfFNCfxvLRAxBrNtf
Example Output: NCfxvLRAxB

Example Input: EOwHDdhJcP, DrIuDdhJYw
Example Output: DdhJ

Example Input: qADKhbsHhAE, JEKhbsEcb
Example Output:
Khbs