The second question is easy to do. According to the meaning of the question, it can be divided into 996 groups, that is to say, there are 996 sums, in which 1000- 1002 has an odd number, the sum is an odd number, and1001003 has two odd numbers. An even number, the sum is even, and the following sum is odd and even, so the odd sum is 996/2=498.