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

YlhtTQgHiffTbIbBrcHMqFKCdWz, HyregFgMffTbIbBrcHYUnnQvGlx
ffTbIbBrcH

spGRUmIYuGl, qkqRUmItqU
RUmI

TSJhvfaddJP, oVhvfafSJs

hvfa