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

[EX Q]: jLbHvZmecfxMcGLXGVsO, erFBGmecfxMcJtDyKGZ
[EX A]: mecfxMc

[EX Q]: bmZKWkYPqugcvzbHykblPzQLhK, tPUzKqugcvzbHypzk
[EX A]: qugcvzbHy

[EX Q]: RPeJeuMqdeeWFSwpBNdzr, VvEbRXEuteuMqdeeWFsxsokaD
[EX A]:
euMqdeeWF