1。 Every four numbers are a period, such as 12-3-4, and the sum of each period is -4, * * 50 1 period, so what is 50 1*-4=-2004?

()2。 1。 . . . When 2004 is all positive numbers, the sum is 1002*2005, and its value is even, but it is not considered when adding symbols. When a minus sign is added, its value is1002 * 2005-2 * n.

(For example, 2+3+4-5=2+3+4+5-2*5) is obviously an even number. (odd sum or difference is odd, even sum or difference is even)