from itertools import *
def f(x, y, z, w):
    return (x <= y and (not(z))) or w
for a1, a2, a3, a4, a5, a6 in product([0, 1], repeat = 6 ):
    table = [(a1, a2, 1, 0), (0, a3, a4, 1), (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)