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

[EX Q]: oHoJrr, YAoJSq
[EX A]: oJ

[EX Q]: XpFCxFOgTTNCnQzMnVPV, FMqzdOwgTTNCnQzedorxVPe
[EX A]: gTTNCnQz

[EX Q]: nYoRQU, gQoRZQ
[EX A]:
oR