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

Example Input: VRXUhOYfTul, JqZUhOYKq
Example Output: UhOY

Example Input: SJIkEibGrqcrOBgGjYjJc, EervOGrqcrOBgGJZyx
Example Output: GrqcrOBgG

Example Input: aYLiOyLTwy, PjWiOyLTXOzuU
Example Output:
iOyLT