Solving longest common subsequence from a set of words

lcs.py

""" A snippet for calculating longest subsequence of list of words
"""
import re

# copy and paste seperation into here

INPUT = filter(len, """
fuad-not-distressed
arrows_counterclockwise
""".split('\n'))

# other test input
#INPUT_0122 = filter(len, re.split(r'\s', ":flashlight: :hulk_smash: :flag-sh: :camera_with_flash:"))

def lcs(X, Y, m=None, n=None):
    # print((X, Y, m, n))
    if m is None:
        m = len(X)
    if n is None:
        n = len(Y)
    if m == 0 or n == 0:
        return ""
    elif X[m-1] == Y[n-1]:
        return lcs(X, Y, m-1, n-1) + X[m-1]
    else:
        x_lcs = lcs(X, Y, m, n-1)
        y_lcs = lcs(X, Y, m-1, n)
        return x_lcs if len(x_lcs) > len(y_lcs) else y_lcs


if __name__ == "__main__":
    print(INPUT)

    # pre filter since above could be O(n^2) operation!
    agreed_chars = set.intersection(*map(set, INPUT))
    print("Agreed set: {}".format(agreed_chars))

    filtered_inputs = map(
        lambda s: "".join([c for c in s if c in agreed_chars]),
        INPUT
    )
    print("Filtered input: {}".format(filtered_inputs))

    last_lcs = ""
    for i in range(len(filtered_inputs)-1):
        last_lcs = lcs(filtered_inputs[i], filtered_inputs[i+1])
        print("Last result is: {}".format(last_lcs))

    print("Final LCS: {}".format(last_lcs))