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: yKtQOhYvrJVH, HQsTQOhYvPP
Example Output: QOhYv

Example Input: xLdMATwfcTAfpczyy, LRtTwfcTAuR
Example Output:
TwfcTA