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

Example Input: uGDJixAmSiVaFRmfKRM, NsTGxsJixAmSiVageSw
Example Output: JixAmSiVa

Example Input: hcmMoVBhK, mdmMoVBjuT
Example Output: mMoVB

Example Input: fBpRXPkikQokGVeS, FwUbKXkikQokGos
Example Output:
kikQokG