Gates: NAND
	NAND gate: implements NAND (negated AND) function
	Input: 2 bits
	Output: 1 bit
	Truth table:						Symbol:
		Input		Output
		x0	x1	z
		0	0	1
		0	1	1
		1	0	1
		1	1	0
			z = x0 NAND x1
	Properties:
	symmetric:		x NAND y = y NAND x
	not associative
	n inputs:
		NANDn (x0, x1, . . . , xn) = NOT (x0 * x1 * . . . xn)