Sergey wrote
PARTS:
    // Put your code here:
        Nand (a=a, b=b, out=outnot);
        Not (in=outnot, out=out);
}
Code is working. I test it. Problem again in Not. Need use buil-in Not.
 
His problem has NOTHING to do with the Not gate and using the built-in Not gate would have changed NOTHING.