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

Example Input: yJRITYgVTSNsPjG, NSIdKYgVTSNmj
Example Output: YgVTSN

Example Input: oKZCAErEMqzODnkcNqxVdoBOC, yHzRJuSqzODnkcNqxExr
Example Output: qzODnkcNqx

Example Input: dBwcwyTCiJMvNOFyGYOTCmkjJCyd, HZHpvUMvNOFyGYOTecuh
Example Output:
MvNOFyGYOT