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