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

Example Input: inquDFuJxtBaaFGCaRzO, NYcnWDuDFuJxtBafxZWCUw
Example Output: uDFuJxtBa

Example Input: YCAyruPTTHWhCYaiXfIl, OETdzqAyruPTTHWgS
Example Output: AyruPTTHW

Example Input: ScWsrkkRDpALgoUBe, McdDMObsrkkRDpPPwb
Example Output:
srkkRDp