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

Input: Consider Input: spGRUmIYuGl, qkqRUmItqU

Output: RUmI

Input: Consider Input: SJIkEibGrqcrOBgGjYjJc, EervOGrqcrOBgGJZyx

Output: GrqcrOBgG

Input: Consider Input: XorFVxhmNjraFW, edxhmNjKKnUi
Output: xhmNj