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

Example Input: MSxTzCpiJAplpzSvLlNJS, oScCpiJAplpNVrqkn
Example Output: CpiJAplp

Example Input: RinootTGLjbRGYznmBdH, oRMtTGLjbRGYzwEVHsjW
Example Output: tTGLjbRGYz

Example Input: ElpcLeitDHRtXeiwzF, cYdaFzMtDHRtXeCt
Example Output:
tDHRtXe