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

Example Input: GnElFKBIoYmAdvz, GrElFKBIoMo
Example Output: ElFKBIo

Example Input: PQCjJwXurLeN, vsjJwXuOy
Example Output: jJwXu

Example Input: lWsEQdhP, IFEQdMc
Example Output:
EQd