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

[EX Q]: TnHJcxtwcZ, XFdHJcxNKw
[EX A]: HJcx

[EX Q]: VTwtMVKmrRvL, WLoVtWtMVKmrDCke
[EX A]: tMVKmr

[EX Q]: QMYGDgxDeJCer, tlIfcxlYGDgxDeFPzsrT
[EX A]:
YGDgxDe