In this task, you are given two lists A,B. Find the longest common subsequence in the lists A and B.
[2251, 'n', 7249, 2551, 6039, '6341', 'l', '7951', '603', '5783', 'V', 6931, 7737, 5509], [6923, 'J', 'N', '6341', 'l', '7951', '603', '5783', 'U', 'O', 2891, 3223, 8449]