from itertools import *
def f(x, y, z, w):
    return (x and (not(y))) or (x == z) or w
for a1, a2, a3, a4, a5, a6 in product([0, 1], repeat = 6 ):
    table = [(1, a1, a2, 1), (a3, 0, a4, 0), (1, a5, 1, a6)]
    if len(table) == len(set(table)):
        for p in permutations('xywz'):
            if [f(**dict(zip(p, r))) for r in table] == [0, 0, 0]:
                print(p)