The absolute value of x is 1 x= 1 or-1.
x？ -(a+b+c * d) x-c * d = 1-x-1=-x = plus or minus1.
2. If A, B and C are three arbitrary integers, there are four cases of parity.
If (1) is even, then (a+b)/2, (b+c)/2 and (c+a)/2 are all integers.
(2) The parity rules (a+b)/2, (b+c)/2 and (c+a)/2 have only one integer.
(3) The parity rules (a+b)/2, (b+c)/2 and (c+a)/2 have only one integer.
(4) If they are all even numbers, then (a+b)/2, (b+c)/2 and (c+a)/2 are all integers.
∴ There are at least 1 integers in the three numbers.
3.99 12/ 13 times minus thirteen = 99 × (-13)+12/13 =-/kloc-0.