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

Example Input: wkVVZREWhcSCpvCTB, ZQWhcSCpvCDVUY
Example Output: WhcSCpvC

Example Input: BICndZkjoSidWivWATvtqsS, FzVWjoSidWivFaQhkRT
Example Output: joSidWiv

Example Input: kKducIq, IVducvdx
Example Output:
duc