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

Example Input: OYERnjubLFovtcS, FngzQJVGERnjubLFafmzq
Example Output: ERnjubLF

Example Input: gTjTwC, OUjTgM
Example Output: jT

Example Input: ELjnQGFRjuUyjMl, SWZKbcFRjuUyjfAE
Example Output:
FRjuUyj