Travis wanted to relax and took a walk round the town's pubs.
Sitting at the first pubs, he realized that walking round the pubs one
after another was not interesting at all, so he numbered all the pubs
in the town from 1 to n starting from the pub he was sitting in
and decided to move from one pub to another only if the number of one of them
divided the number of the other. Naturally, Travis wanted to know how many pubs
he could visit if he followed this rule and didn't visit any pub more than
Why would Travis be up to such a strange amusement? The point is that he
is a louse living on the head of the eccentric mathematician Professor Pilgarlic.
Help Professor and his little friend answer the intriguing question.
The only input line contains the number n of pubs in the town
(2 ≤ n ≤ 50).
In the first line output the maximal number of pubs Travis can visit. In the
second line, output the numbers of these pubs separated with a space
in the order of visiting. Remember that the route must start at the first pub.
If there are several solutions, output any of them.
1 9 3 6 2 4 8
Problem Author: Ekaterina Vasilyeva
Problem Source: XI USU Open Personal Contest (March 13, 2010)