def main(field in1, field in2, field in3, field in4, field in5, field in6, field in7, field in8) -> field {
    // first iteration
    field a = (in1 + in2) / 2;
    field b = (in3 + in4) / 2;
    field c = (in5 + in6) / 2;
    field d = (in7 + in8) / 2;
    field e = (in1 - in2) / 2;
    field f = (in3 - in4) / 2;
    field g = (in5 - in6) / 2;
    field h = (in7 - in8) / 2;
    // second iteration
    field i = (a + b) / 2;
    field j = (c + d) / 2;
    field k = (e - f) / 2;
    field l = (g - h) / 2;
    // third iteration
    field out1 = (i + j) / 2;
    return (k - l) / 2;
}