In this task, you are given two lists A,B. Find the longest common subsequence in the lists A and B.
[7643, 'b', 'i', 5419, 6149, '6053', 'H', '9575', 'Q', 'Y', '5507', 'm', '3081', 'D', 5713, 907, 1839, 6947], [7397, 'B', 'x', 8321, 'L', 'a', '6053', 'H', '9575', 'Q', 'Y', '5507', 'm', '3081', 'm', 1961, 5519]