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

Example Input: KKebLWQCQzVIojj, nxQCQzVIopD
Example Output: QCQzVIo

Example Input: zqRbqwgmqGIAGTeeoGFOSr, RFnLqwgmqGIAGLcEvAWxY
Example Output: qwgmqGIAG

Example Input: ljCkuMhdxIZrKevfxYbPpwjCy, KXSkSOwIZrKevfxYoRLmmtZ
Example Output:
IZrKevfxY