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

Example Input: NUuLSmDjCKcJPc, lGGSLIDjCKcJBo
Example Output: DjCKcJ

Example Input: YHLJZrFQ, aSLJZQuo
Example Output: LJZ

Example Input: GnElFKBIoYmAdvz, GrElFKBIoMo
Example Output:
ElFKBIo