Codeforces Round 988 (Div. 3) |
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Finished |
Superultra, a little red panda, desperately wants primogems. In his dreams, a voice tells him that he must solve the following task to obtain a lifetime supply of primogems. Help Superultra!
Construct a permutation$$$^{\text{∗}}$$$ $$$p$$$ of length $$$n$$$ such that $$$p_i + p_{i+1}$$$ is composite$$$^{\text{†}}$$$ over all $$$1 \leq i \leq n - 1$$$. If it's not possible, output $$$-1$$$.
$$$^{\text{∗}}$$$A permutation of length $$$n$$$ is an array consisting of $$$n$$$ distinct integers from $$$1$$$ to $$$n$$$ in arbitrary order. For example, $$$[2,3,1,5,4]$$$ is a permutation, but $$$[1,2,2]$$$ is not a permutation ($$$2$$$ appears twice in the array), and $$$[1,3,4]$$$ is also not a permutation ($$$n=3$$$ but there is $$$4$$$ in the array).
$$$^{\text{†}}$$$An integer $$$x$$$ is composite if it has at least one other divisor besides $$$1$$$ and $$$x$$$. For example, $$$4$$$ is composite because $$$2$$$ is a divisor.
The first line contains $$$t$$$ ($$$1 \leq t \leq 10^4$$$) — the number of test cases.
Each test case contains an integer $$$n$$$ ($$$2 \leq n \leq 2 \cdot 10^5$$$) — the length of the permutation.
It is guaranteed that the sum of $$$n$$$ over all test cases does not exceed $$$2 \cdot 10^5$$$.
For each test case, if it's not possible to construct $$$p$$$, output $$$-1$$$ on a new line. Otherwise, output $$$n$$$ integers $$$p_1, p_2, \ldots, p_n$$$ on a new line.
238
-1 1 8 7 3 6 2 4 5
In the first example, it can be shown that all permutation of size $$$3$$$ contain two adjacent elements whose sum is prime. For example, in the permutation $$$[2,3,1]$$$ the sum $$$2+3=5$$$ is prime.
In the second example, we can verify that the sample output is correct because $$$1+8$$$, $$$8+7$$$, $$$7+3$$$, $$$3+6$$$, $$$6+2$$$, $$$2+4$$$, and $$$4+5$$$ are all composite. There may be other constructions that are correct.
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