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

Example Input: HiEuutntEBpU, fdkqEuutntEBABdGZRND
Example Output: EuutntEB

Example Input: OYERnjubLFovtcS, FngzQJVGERnjubLFafmzq
Example Output: ERnjubLF

Example Input: JMBTxqs, KdcBTxQKq
Example Output:
BTx