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

[EX Q]: VLxrvK, gvxrac
[EX A]: xr

[EX Q]: wbFDXJQDQxQJzudOUlR, QEbsIDXJQDQxQsSYIutwU
[EX A]: DXJQDQxQ

[EX Q]: tqOdIYTjdF, etlwOdIYyUiO
[EX A]:
OdIY