In this task, you are given two lists A,B. Find the longest common subsequence in the lists A and B.
[3991, 'n', 'n', 'M', 7889, 9165, 1293, 'r', 'P', '721', 'N', '4617', 'W', '5913', 's', '5073', '9913', 'g', 'K', 'q', 109, 1845], ['e', 'r', 'Y', 8285, 'r', 'P', '721', 'N', '4617', 'W', '5913', 's', '5073', '9913', 'g', 'S', 915, 'T', 'I', 8115, 2873, 'x']