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

[Q]: OyrqfQQnzOFUzrkDM, iBkQQnzOFewhjvO
[A]: QQnzOF


[Q]: cfvqbAUpWEmhCSFaUvGrYVNGeUiRP, hAxWMEmhCSFaUvGLBLmdTxhy
[A]: EmhCSFaUvG


[Q]: mHQRtGpHA, coRtGud
[A]:
RtG