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: jLbHvZmecfxMcGLXGVsO, erFBGmecfxMcJtDyKGZ
Example Output: mecfxMc

Example Input: WBUJqkQcGcFyFU, ENaBOJqkQcGcmd
Example Output:
JqkQcGc