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

Example Input: bUcuzFgsdfojVR, IdcuzFgsdMRgtMA
Example Output: cuzFgsd

Example Input: UldKHMpUYADGfEUGcSon, nPHMpUYADGfEKqHCLPmL
Example Output: HMpUYADGfE

Example Input: okrSHnTsitq, DtXXHnTsiNe
Example Output:
HnTsi