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

Example Input: bOvlVNWf, iivlVzWt
Example Output: vlV

Example Input: tWJoKSOAuVhmsomA, emdmnBFJoKSOAuVzSgW
Example Output: JoKSOAuV

Example Input: pYaEyEY, qRuaEyAjh
Example Output:
aEy