#948. n queens
In how many ways can you place n queens on an n×n board so that no two queens attack each other?
### Input
One integer n (1 ≤ n ≤ 8).
### Output
A number.
Examples
Input
4
Output
2
Input
7
Output
40
💡 You can solve it with Python, JavaScript or blocks. Read the input line by line with input(). Don't print a question (like input("Number: ")). Print exactly what the output asks for, nothing more.