A puzzle about queens

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Vasya recently started playing chess and somewhere read a puzzle in which it was necessary to place the maximum number of queens on an $8 \times 8$ board so that at least one square remained unattacked. This problem is easily solved for a $3 \times 3$ board, since it is clear that it is impossible to place more than two queens on it in this way. Help Vasya solve this problem for an $N \times N$ board.

Input Format

The input contains a natural number $N$ -- the size of the chessboard $N \times N$ $(1 \le N \le 100)$.

Output Format

In the output, you need to print the maximum number of queens that can be placed on an $N \times N$ chessboard so that one square remains unattacked.

3

2