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

Example Input: kOrQWjLKnwN, xFsWjLKgr
Example Output: WjLK

Example Input: OezHeoe, ouUzHemU
Example Output: zHe

Example Input: zcNDvTxCdAFRDMnKpJCH, yDJDaYZgxCdAFRDMnvIyUmVji
Example Output:
xCdAFRDMn