（1998/1-1）（1997/1-1）（1996/1-1）...（1001/1-1）（1000/1-1） Wrong, the numerator is 1, the denominator is 1998, everything else is

If 1 is changed into 1998 / 1998, the first term is - 1997 / 1998
So the final result is - 999 / 1998, that is - 1 / 2

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