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

[EX Q]: SIIPePlrkftKkzfgdjg, JqNnXHrkftKkzOMUwmc
[EX A]: rkftKkz

[EX Q]: XjYkMfARxWBSBjuXyDrFt, EtUxIfiHkMfARxWBSckTLTTnR
[EX A]: kMfARxWBS

[EX Q]: mgZHYBNnFcRitgAvWjKYKP, MlCiMWFcRitgAvzwoxZRMj
[EX A]:
FcRitgAv