A book consists of odd pages and even pages. For example, 1 is odd and 2 is even. Then we can regard the first and second pages as a whole, as well as the third and fourth pages. How many pages are there like this? The title says, 397, that's 794 numbers, but there is another situation, for example, the last page is odd, for example, page 333, she can't form a partner without friends, right? Then add her, that's 795, so the answer is 794 or 795.