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

Example Input: bmZKWkYPqugcvzbHykblPzQLhK, tPUzKqugcvzbHypzk
Example Output: qugcvzbHy

Example Input: DZfOjrQffR, CXOjrQQc
Example Output: OjrQ

Example Input: HVVozpGyQNw, bAVozpGyzWRyl
Example Output:
VozpGy