You have to place N queens on an N-by-N chessboard in a way that no two queens attack each other.
The rule is that each row, column, and diagonal of the board contains exactly one queen.
Your mission is to compute how many possible ways to place N queens on that chessboard.
An integer N that represents the size of chessboard and the number of queens.
where 1<=N<=10
An integer that represents the number of possible placements of N queens.
There is no need to add '\n' at the end of output