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

Example Input: SJIkEibGrqcrOBgGjYjJc, EervOGrqcrOBgGJZyx
Example Output: GrqcrOBgG

Example Input: NTINFnRckGsfLqhSoA, UUONcKKFnRckGsfLqVak
Example Output: FnRckGsfLq

Example Input: wnbqKbzvpAC, PrKbzvpucdE
Example Output:
Kbzvp