from itertools import *
def f(x, y, z, w):
    return (x or not(y)) and not(y == z) and w
for a1, a2, a3, a4 in product([0, 1], repeat = 4):
    table = [(0, 1, a1, 0), (a2, 1, 1, 0), (1, a3, 0, a4)]
    if len(table) == len(set(table)):
        for p in permutations('xywz'):
            if [f(**dict(zip(p, r))) for r in table] == [1, 1, 1]:
                print(p)