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

SOLUTION: eqnu

PROBLEM: NUuLSmDjCKcJPc, lGGSLIDjCKcJBo

SOLUTION: DjCKcJ

PROBLEM: uTwuwS, QJwuDV

SOLUTION:
wu