(1/2003-1)(1/2002-1)(1/2001-1)...*(1/1001-1)(1/1000-1)

1/2003-1=-2002/20031/2002-1=-2001/20021/2001-1=-2000/2001...1/1001-1=-1000/10011/1000-1=-999/1000因为共有2003-1000+1=1004个负数相乘,所以结果为正得：2002/2003×2001/2002×2000/2001×……×1000/1001×99...