A8906. Permutation Sum
编程题
普及/提高-
知识点
题目描述
Permutation $p$ is an ordered set of integers $p_{1},p_{2},...,p_{n}$ , consisting of $n$ distinct positive integers, each of them doesn't exceed $n$ . We'll denote the $i$ -th element of permutation $p$ as $p_{i}$ . We'll call number $n$ the size or the length of permutation $p_{1},p_{2},...,p_{n}$ .
Petya decided to introduce the sum operation on the set of permutations of length $n$ . Let's assume that we are given two permutations of length $n$ : $a_{1},a_{2},...,a_{n}$ and $b_{1},b_{2},...,b_{n}$ . Petya calls the sum of permutations $a$ and $b$ such permutation $c$ of length $n$ , where $c_{i}=((a_{i}-1+b_{i}-1)\ mod\ n)+1$ $(1<=i<=n)$ .
Operation  means taking the remainder after dividing number $x$ by number $y$ .
Obviously, not for all permutations $a$ and $b$ exists permutation $c$ that is sum of $a$ and $b$ . That's why Petya got sad and asked you to do the following: given $n$ , count the number of such pairs of permutations $a$ and $b$ of length $n$ , that exists permutation $c$ that is sum of $a$ and $b$ . The pair of permutations $x,y$ $(x≠y)$ and the pair of permutations $y,x$ are considered distinct pairs.
As the answer can be rather large, print the remainder after dividing it by $1000000007$ ( $10^{9}+7$ ).
Petya decided to introduce the sum operation on the set of permutations of length $n$ . Let's assume that we are given two permutations of length $n$ : $a_{1},a_{2},...,a_{n}$ and $b_{1},b_{2},...,b_{n}$ . Petya calls the sum of permutations $a$ and $b$ such permutation $c$ of length $n$ , where $c_{i}=((a_{i}-1+b_{i}-1)\ mod\ n)+1$ $(1<=i<=n)$ .
Operation  means taking the remainder after dividing number $x$ by number $y$ .
Obviously, not for all permutations $a$ and $b$ exists permutation $c$ that is sum of $a$ and $b$ . That's why Petya got sad and asked you to do the following: given $n$ , count the number of such pairs of permutations $a$ and $b$ of length $n$ , that exists permutation $c$ that is sum of $a$ and $b$ . The pair of permutations $x,y$ $(x≠y)$ and the pair of permutations $y,x$ are considered distinct pairs.
As the answer can be rather large, print the remainder after dividing it by $1000000007$ ( $10^{9}+7$ ).
输入格式
The single line contains integer $n\ (1<=n<=16)$ .
输出格式
In the single line print a single non-negative integer — the number of such pairs of permutations $a$ and $b$ , that exists permutation $c$ that is sum of $a$ and $b$ , modulo $1000000007$ ( $10^{9}+7$ ).
输入输出样例
输入 #1
3
输出 #1
18
输入 #2
5
输出 #2
1800