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

[EX Q]: nYoRQU, gQoRZQ
[EX A]: oR

[EX Q]: XYnCjAWPHHJ, gmCjAWPHpmwVsm
[EX A]: CjAWPH

[EX Q]: XiWtYKbfT, fBttYKIjX
[EX A]:
tYK