from itertools import *
def f(a, b, c, d):
    return ((not(a)) and (not(b))) or (b == c) or d
for a1, a2, a3, a4 in product([0, 1], repeat = 4):
    table = [(a1, a2, 1, a3), (1, 0, a4, 1), (0, 0, 1, 1)]
    if len(table) == len(set(table)):
        for p in permutations('abcd'):
            if [f(**dict(zip(p, r))) for r in table] == [0, 0, 0]:
                print(p)