def lcs(strA, strB):
    """Determine the length of the Longest Common Subsequence of 2 strings."""
    if len(strA) == 0 or len(strB) == 0:
        return 0
    if strA[-1] == strB[-1]: 
        return 1 + lcs(strA[:-1], strB[:-1])
    return max(lcs(strA[:-1], strB), lcs(strA, strB[:-1]))