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

[EX Q]: iupYjFXrrMqWzJSLUSwmEukHc, hqajjWrrMqWzJSLnF
[EX A]: rrMqWzJSL

[EX Q]: lrBJDRkT, jmBJDrI
[EX A]: BJD

[EX Q]: EZvYJy, qHvYEd
[EX A]:
vY