from itertools import *
def f(x, y, z, w):
    return (x and not(y)) or (x == z) or w
for a in product([0,1], repeat = 4):
    table = [(1, a[0], 0, 0), (1, 1, a[1], 0), (a[2], 1, 1, a[3])]
    if len(table) == len(set(table)):
        for p in permutations('xyzw'):
            if [f(**dict(zip(p, r))) for r in table] == [0, 0, 0]:
                print(p)