TASK DEFINITION: In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
PROBLEM: SQNzngllNbOkKDK, MijfNzngllNDfWge

SOLUTION: NzngllN

PROBLEM: wCfNCfxvLRAxBstRTwMSqTn, AhwxfFNCfxvLRAxBrNtf

SOLUTION: NCfxvLRAxB

PROBLEM: HEVqGddewrNqiZ, iyvlddewrNXr

SOLUTION:
ddewrN