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

Q: XZslQqrShfCXRXyHrFVq, BtOQgQqrShfCXRRCRbMvXPM

A: QqrShfCXR
****
Q: TvNVpHLPYjBCeUpyxlzFZ, tgKdPKVYjBCeUpyPK

A: YjBCeUpy
****
Q: auDKDgjnT, QlKDgwC

A:
KDg
****