def simple(a):
    pass


def bit_more_complex(a):
    pass


def two_inputs_bit_more_complex(a, b):
    pass


def many_inputs_bit_more_complex(a, b, c, d, e, f):
    pass


def three_inputs_bit_more_complex(a, b, c):
    pass


def solve_iris(x1, x2, x3, x4):
    pass
