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

Example Input: TTagIJmzrOTdnKr, UONmtdHJmzrOTduWo
Example Output: JmzrOTd

Example Input: OyXwTWbLByC, yODnTWbLWYzc
Example Output: TWbL

Example Input: yYsrWoQLdEeXrXbnGZAz, JHwLdEeXrXvcTnsKe
Example Output:
LdEeXrX