Codeforces Round 716 (Div. 2) |
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Finished |
Now you get Baby Ehab's first words: "Given an integer $$$n$$$, find the longest subsequence of $$$[1,2, \ldots, n-1]$$$ whose product is $$$1$$$ modulo $$$n$$$." Please solve the problem.
A sequence $$$b$$$ is a subsequence of an array $$$a$$$ if $$$b$$$ can be obtained from $$$a$$$ by deleting some (possibly all) elements. The product of an empty subsequence is equal to $$$1$$$.
The only line contains the integer $$$n$$$ ($$$2 \le n \le 10^5$$$).
The first line should contain a single integer, the length of the longest subsequence.
The second line should contain the elements of the subsequence, in increasing order.
If there are multiple solutions, you can print any.
5
3 1 2 3
8
4 1 3 5 7
In the first example, the product of the elements is $$$6$$$ which is congruent to $$$1$$$ modulo $$$5$$$. The only longer subsequence is $$$[1,2,3,4]$$$. Its product is $$$24$$$ which is congruent to $$$4$$$ modulo $$$5$$$. Hence, the answer is $$$[1,2,3]$$$.
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