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

Example Input: ICizmXnKMpUH, oDrnmXnKgWXX
Example Output: mXnK

Example Input: OBzHWjmkcgVGPyv, gCHWjmkcgVMq
Example Output: HWjmkcgV

Example Input: WAogyDOjJUAxTm, RNVFgyDOjJTg
Example Output:
gyDOjJ